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Cerdido S, Abrisqueta M, Sánchez-Beltrán J, Lambertos A, Castejón-Griñán M, Muñoz C, Olivares C, García-Borrón JC, Jiménez-Cervantes C, Herraiz C. MGRN1 depletion promotes intercellular adhesion in melanoma by upregulation of E-cadherin and inhibition of CDC42. Cancer Lett 2024; 581:216484. [PMID: 38008393 DOI: 10.1016/j.canlet.2023.216484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 10/25/2023] [Accepted: 11/03/2023] [Indexed: 11/28/2023]
Abstract
Mahogunin Ring Finger 1 is an E3-ubiquitin ligase encoded by the color gene MGRN1. Our previous in vitro and in vivo studies demonstrated that Mgrn1 deletion in mouse melanoma cells induced cell differentiation and adhesion, and decreased cell motility and invasion on collagen I, and lung colonization in an in vivo model. Here, we investigated the role of MGRN1 on human melanoma cell morphology, adhesion and expression of genes/proteins involved in an EMT-like transition. We demonstrated that wild-type BRAF human melanoma cells adopted a clustering-like morphology on collagen I, with permanent MGRN1 abrogation resulting in bigger cell clusters. Enhanced intercellular adhesion was mostly mediated by induction of E-cadherin and higher co-localization with β-catenin. Transcriptional upregulation of E-cadherin likely occurred through downregulation of the ZEB1 repressor. Finally, pulldown assays showed reduced activation of CDC42 in the absence of MGRN1, which was reverted after E-cadherin silencing. Overall, these findings highlight a new MGRN1-dependent pathway regulating melanoma cell shape, motility, and invasion potential.
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Affiliation(s)
- S Cerdido
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - M Abrisqueta
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - J Sánchez-Beltrán
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - A Lambertos
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - M Castejón-Griñán
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - C Muñoz
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - C Olivares
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - J C García-Borrón
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - C Jiménez-Cervantes
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain
| | - C Herraiz
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB), 30120, Murcia, Spain.
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Nakadate K, Kawakami K. Immunohistochemical and Immunoelectron Microscopical Distribution of MEGF8 in the Mouse Central Nervous System. Cells 2023; 13:63. [PMID: 38201267 PMCID: PMC10778434 DOI: 10.3390/cells13010063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/20/2023] [Accepted: 12/25/2023] [Indexed: 01/12/2024] Open
Abstract
Mutations in multiple epidermal growth factor-like domain 8 (MEGF8), a multidomain transmembrane protein encoded by a gene conserved across species, cause Carpenter's syndrome, which is associated with learning disabilities, mental health issues, and left-right patterning abnormalities. MEGF8 interacts with MGRN1, a protein that functions as an E3 ubiquitin ligase and is involved in multiple physiological and pathological processes. However, the mechanism underlying the distribution of MEGF8 in the central nervous system (CNS) and its cellular and subcellular locations remain unknown. This study aimed to map MEGF8 in the mouse CNS using a new antibody. We discovered that MEGF8 was distributed in the majority of neuronal cell somata across most CNS regions. High levels of MEGF8 were expressed in the neuropils of the CNS gray matter. Immunoelectron microscopy showed that MEGF8 was present in the synapses and around the outer mitochondrial membrane. These findings show that MEGF8 is uniformly distributed throughout the mouse CNS, and its distribution indicates that it plays a substantial role in synaptic and mitochondrial functions. To the best of our knowledge, this is the first study to document MEGF8 distribution in the CNS.
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Affiliation(s)
- Kazuhiko Nakadate
- Department of Basic Science, Educational and Research Center for Pharmacy, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose 204-8588, Tokyo, Japan;
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Distribution and Localization of Mahogunin Ring Finger 1 in the Mouse Central Nervous System. Int J Mol Sci 2022; 23:ijms23168956. [PMID: 36012221 PMCID: PMC9408835 DOI: 10.3390/ijms23168956] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/05/2022] [Accepted: 08/10/2022] [Indexed: 11/16/2022] Open
Abstract
Mahogunin ring finger 1 (MGRN1), an E3 ubiquitin, is involved in several physiological and neuropathological processes. Although mgrn1 mRNA is widely distributed in the central nervous system (CNS), detailed information on its cellular and subcellular localization is lacking and its physiological role remains unclear. In this study, we aimed to determine the distribution of MGRN1 in the mouse CNS using a newly produced antibody against MGRN1. We found that the MGRN1 protein was expressed in most neuronal cell bodies. An intense MGRN1 expression was also observed in the neuropil of the gray matter in different regions of the CNS, including the main olfactory bulb, cerebral cortex, caudate, putamen, thalamic nuclei, hypothalamic nuclei, medial eminence, superior colliculus, hippocampus, dentate gyrus, and spinal cord. Contrastingly, no MGRN1 expression was observed in glial cells. Double fluorescence and immunoelectron microscopic analyses revealed the intracellular distribution of MGRN1 in pre-synapses and near the outer membrane of the mitochondria in neurons. These findings indicate that MGRN1 is more widely expressed throughout the CNS; additionally, the intracellular expression of MGRN1 suggests that it may play an important role in synaptic and mitochondrial functions.
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Abrisqueta M, Cerdido S, Sánchez-Beltrán J, Martínez-Vicente I, Herraiz C, Lambertos A, Olivares C, Sevilla A, Alonso S, Boyano MD, García-Borrón JC, Jiménez-Cervantes C. MGRN1 as a Phenotypic Determinant of Human Melanoma Cells and a Potential Biomarker. LIFE (BASEL, SWITZERLAND) 2022; 12:life12081118. [PMID: 35892921 PMCID: PMC9331370 DOI: 10.3390/life12081118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/15/2022] [Accepted: 07/21/2022] [Indexed: 11/18/2022]
Abstract
Mahogunin Ring Finger 1 (MGRN1), a ubiquitin ligase expressed in melanocytes, interacts with the α melanocyte-stimulating hormone receptor, a well-known melanoma susceptibility gene. Previous studies showed that MGRN1 modulates the phenotype of mouse melanocytes and melanoma cells, with effects on pigmentation, shape, and motility. Moreover, MGRN1 knockdown augmented the burden of DNA breaks in mouse cells, indicating that loss of MGRN1 promoted genomic instability. However, data concerning the roles of MGRN1 in human melanoma cells remain scarce. We analyzed MGRN1 knockdown in human melanoma cells. Transient MGRN1 depletion with siRNA or permanent knockdown in human melanoma cells by CRISPR/Cas9 caused an apparently MITF-independent switch to a more dendritic phenotype. Lack of MGRN1 also increased the fraction of human cells in the S phase of the cell cycle and the burden of DNA breaks but did not significantly impair proliferation. Moreover, in silico analysis of publicly available melanoma datasets and estimation of MGRN1 in a cohort of clinical specimens provided preliminary evidence that MGRN1 expression is higher in human melanomas than in normal skin or nevi and pointed to an inverse correlation of MGRN1 expression in human melanoma with patient survival, thus suggesting potential use of MGRN1 as a melanoma biomarker.
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Affiliation(s)
- Marta Abrisqueta
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
| | - Sonia Cerdido
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
| | - José Sánchez-Beltrán
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
| | - Idoya Martínez-Vicente
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
| | - Cecilia Herraiz
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
| | - Ana Lambertos
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
| | - Conchi Olivares
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
| | - Arrate Sevilla
- Department of Cell Biology and Histology, Faculty of Medicine and Nursing, University of Basque Country UPV/EHU, 48940 Leioa, Spain; (A.S.); (M.D.B.)
| | - Santos Alonso
- Department of Genetics, Physical Anthropology and Animal Physiology, Faculty of Science and Technology, UPV/EHU, University of Basque Country UPV/EHU, 48940 Leioa, Spain;
| | - María Dolores Boyano
- Department of Cell Biology and Histology, Faculty of Medicine and Nursing, University of Basque Country UPV/EHU, 48940 Leioa, Spain; (A.S.); (M.D.B.)
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
| | - José Carlos García-Borrón
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
| | - Celia Jiménez-Cervantes
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia, LAIB Building, Room 1.53, Campus de Ciencias de la Salud, Carretera Buenavista s/n, 30120 Murcia, Spain; (M.A.); (S.C.); (J.S.-B.); (I.M.-V.); (C.H.); (A.L.); (C.O.); (J.C.G.-B.)
- Biomedical Research Institute of Murcia (Instituto Murciano de Investigación Biosanitaria, IMIB), 30120 Murcia, Spain
- Correspondence:
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D'Silva S, Chakraborty S, Kahali B. Concurrent outcomes from multiple approaches of epistasis analysis for human body mass index associated loci provide insights into obesity biology. Sci Rep 2022; 12:7306. [PMID: 35508500 PMCID: PMC9068779 DOI: 10.1038/s41598-022-11270-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 04/18/2022] [Indexed: 12/13/2022] Open
Abstract
Genome wide association studies (GWAS) have focused on elucidating the genetic architecture of complex traits by assessing single variant effects in additive genetic models, albeit explaining a fraction of the trait heritability. Epistasis has recently emerged as one of the intrinsic mechanisms that could explain part of this missing heritability. We conducted epistasis analysis for genome-wide body mass index (BMI) associated SNPs in Alzheimer’s Disease Neuroimaging Initiative (ADNI) and followed up top significant interacting SNPs for replication in the UK Biobank imputed genotype dataset. We report two pairwise epistatic interactions, between rs2177596 (RHBDD1) and rs17759796 (MAPK1), rs1121980 (FTO) and rs6567160 (MC4R), obtained from a consensus of nine different epistatic approaches. Gene interaction maps and tissue expression profiles constructed for these interacting loci highlights co-expression, co-localisation, physical interaction, genetic interaction, and shared pathways emphasising the neuronal influence in obesity and implicating concerted expression of associated genes in liver, pancreas, and adipose tissues insinuating to metabolic abnormalities characterized by obesity. Detecting epistasis could thus be a promising approach to understand the effect of simultaneously interacting multiple genetic loci in disease aetiology, beyond single locus effects.
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Affiliation(s)
- Sheldon D'Silva
- Centre for Brain Research, Indian Institute of Science, Bangalore, 560012, India
| | - Shreya Chakraborty
- Centre for Brain Research, Indian Institute of Science, Bangalore, 560012, India.,Interdisciplinary Mathematical Sciences, Indian Institute of Science, Bangalore, 560012, India
| | - Bratati Kahali
- Centre for Brain Research, Indian Institute of Science, Bangalore, 560012, India.
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Lebensohn AM, Bazan JF, Rohatgi R. Receptor control by membrane-tethered ubiquitin ligases in development and tissue homeostasis. Curr Top Dev Biol 2022; 150:25-89. [PMID: 35817504 DOI: 10.1016/bs.ctdb.2022.03.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Paracrine cell-cell communication is central to all developmental processes, ranging from cell diversification to patterning and morphogenesis. Precise calibration of signaling strength is essential for the fidelity of tissue formation during embryogenesis and tissue maintenance in adults. Membrane-tethered ubiquitin ligases can control the sensitivity of target cells to secreted ligands by regulating the abundance of signaling receptors at the cell surface. We discuss two examples of this emerging concept in signaling: (1) the transmembrane ubiquitin ligases ZNRF3 and RNF43 that regulate WNT and bone morphogenetic protein receptor abundance in response to R-spondin ligands and (2) the membrane-recruited ubiquitin ligase MGRN1 that controls Hedgehog and melanocortin receptor abundance. We focus on the mechanistic logic of these systems, illustrated by structural and protein interaction models enabled by AlphaFold. We suggest that membrane-tethered ubiquitin ligases play a widespread role in remodeling the cell surface proteome to control responses to extracellular ligands in diverse biological processes.
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Mahogunin Ring Finger 1 Is Required for Genomic Stability and Modulates the Malignant Phenotype of Melanoma Cells. Cancers (Basel) 2020; 12:cancers12102840. [PMID: 33019669 PMCID: PMC7599452 DOI: 10.3390/cancers12102840] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/25/2020] [Accepted: 09/29/2020] [Indexed: 01/20/2023] Open
Abstract
Simple Summary Melanoma, the most aggressive skin cancer, accounts for the majority of deaths due to this disease. Therefore, identification of genes/proteins involved in melanoma genesis and/or progression is urgent. Mutations abrogating expression of Mahogunin Ring Finger 1 (MGRN1) in mice cause complex phenotypes with hyperpigmentation, and known MGRN1 interactors are important regulators of cell shape and movement. This suggests that MGRN1 may modulate the malignant phenotype of melanoma cells. Analysis of MGRN1-KO mouse melanocytes and melanoma cells showed that lack of MGRN1 leads to cell cycle defects and to a more differentiated, less aggressive phenotype, with increased adhesion to various matrices, decreased motility and high genomic instability. The higher aggressivity of MGRN1-expressing melanoma cells was confirmed in an in vivo mouse melanoma model and is consistent with higher survival of human melanoma patients expressing low levels of MGRN1. Therefore, MGRN1 appears an important determinant of the malignant phenotype of melanoma. Abstract The mouse mahoganoid mutation abrogating Mahogunin Ring Finger-1 (MGRN1) E3 ubiquitin ligase expression causes hyperpigmentation, congenital heart defects and neurodegeneration. To study the pathophysiology of MGRN1 loss, we compared Mgrn1-knockout melanocytes with genetically matched controls and melan-md1 (mahoganoid) melanocytes. MGRN1 knockout induced a more differentiated and adherent phenotype, decreased motility, increased the percentage of cells in the S phase of the cell cycle and promoted genomic instability, as shown by stronger γH2AX labelling, increased burden of DNA breaks and higher abundance of aneuploid cells. Lack of MGRN1 expression decreased the ability of melanocytes to cope with DNA breaks generated by oxidizing agents or hydroxyurea-induced replicative stress, suggesting a contribution of genomic instability to the mahoganoid phenotype. MGRN1 knockout in B16-F10 melanoma cells also augmented pigmentation, increased cell adhesion to collagen, impaired 2D and 3D motility and caused genomic instability. Tumors formed by Mgrn1-KO B16-F10 cells had lower mitotic indices, fewer Ki67-positive cells and showed a trend towards smaller size. In short-term lung colonization assays Mgrn1-KO cells showed impaired colonization potential. Moreover, lower expression of MGRN1 is significantly associated with better survival of human melanoma patients. Therefore, MGRN1 might be an important phenotypic determinant of melanoma cells.
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Martínez-Vicente I, Abrisqueta M, Herraiz C, Jiménez-Cervantes C, García-Borrón JC, Olivares C. Functional characterization of a C-terminal splice variant of the human melanocortin 1 receptor. Exp Dermatol 2020; 29:610-615. [PMID: 32474972 DOI: 10.1111/exd.14118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 05/10/2020] [Accepted: 05/24/2020] [Indexed: 01/08/2023]
Abstract
The melanocortin 1 receptor (MC1R) is a major determinant of skin pigmentation and sensitivity to ultraviolet radiation. When stimulated by its natural agonists, it promotes the switch from synthesis of poorly photoprotective and lightly colored pheomelanins to production of photoprotective and darker eumelanins. In addition to an unusually high number of single nucleotide polymorphisms, the MC1R is expressed as 3 protein-coding splice variants. Two transcripts display different 5' untranslated sequences but yield the same open reading frame corresponding to the canonical 317 aminoacids protein (termed MC1R). An alternative transcript named MC1R-203 encodes for a 382 amino acids protein of poorly characterized functional properties containing an additional 65 aminoacids C-terminal extension. Given the known roles of the MC1R C-terminal extension in forward trafficking, coupling to intracellular effectors and desensitization, the different structure of this domain in MC1R and MC1R-203 may lead to significant functional alteration(s). We have assessed the functional properties of MC1R-203, as compared with the canonical MC1R form. We show that unstimulated HBL human melanoma cells express the MC1R-203 spliceoform, although at much lower levels than canonical MC1R. When expressed in heterologous HEK293 cells, the presence of the 65 aminoacid-long cytosolic extension immediately after Cys316 in MC1R-203 did not impair the intracellular stability of the protein, but it interfered with functional coupling to the cAMP cascade and with the ubiquitylation of ARRB2 associated with MC1R desensitization. Conversely, MC1R-203 retained full capacity to activate ERK1/2 signaling. Accordingly, MC1R-203 displays biased signaling when expressed in HEK293 cells.
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Affiliation(s)
- Idoya Martínez-Vicente
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia and Instituto Murciano de Investigacion Biosanitaria (IMIB), Murcia, Spain
| | - Marta Abrisqueta
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia and Instituto Murciano de Investigacion Biosanitaria (IMIB), Murcia, Spain
| | - Cecilia Herraiz
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia and Instituto Murciano de Investigacion Biosanitaria (IMIB), Murcia, Spain
| | - Celia Jiménez-Cervantes
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia and Instituto Murciano de Investigacion Biosanitaria (IMIB), Murcia, Spain
| | - Jose Carlos García-Borrón
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia and Instituto Murciano de Investigacion Biosanitaria (IMIB), Murcia, Spain
| | - Concepción Olivares
- Department of Biochemistry, Molecular Biology and Immunology, School of Medicine, University of Murcia and Instituto Murciano de Investigacion Biosanitaria (IMIB), Murcia, Spain
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Knockdown of the CXCL12/CXCR7 chemokine pathway results in learning deficits and neural progenitor maturation impairment in mice. Brain Behav Immun 2019; 80:697-710. [PMID: 31100368 DOI: 10.1016/j.bbi.2019.05.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 05/10/2019] [Accepted: 05/13/2019] [Indexed: 12/26/2022] Open
Abstract
In adult brain, the chemokine CXCL12 and its receptors CXCR4 and CXCR7 are expressed in neural progenitor and glial cells. Conditional Cxcl12 or Cxcr4 gene knockout in mice leads to severe alterations in neural progenitor proliferation, migration and differentiation. As adult hippocampal neurogenesis is involved in learning and memory processes, we investigated the long-term effects of reduced expression of CXCL12 or CXCR7 in heterozygous Cxcl12+/- and Cxcr7+/- animals (KD mice) on hippocampal neurogenesis, neuronal differentiation and memory processing. In Cxcl12 KD mice, Cxcr4 mRNA expression was reduced, whereas Cxcr7 was slightly increased. Conversely, in Cxcr7 KD mice, both Cxcr4 and Cxcl12 mRNA levels were decreased. Moreover, Cxcl12 KD animals showed marked behavioral and learning deficits that were associated with impaired neurogenesis in the hippocampus. Conversely, Cxcr7 KD animals showed mild learning deficits with normal neurogenesis, but reduced cell differentiation, measured with doublecortin immunolabeling. These findings suggested that a single Cxcl12 or Cxcr7 allele might not be sufficient to maintain the hippocampal niche functionality throughout life, and that heterozygosity might represent a susceptibility factor for memory dysfunction progression.
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Nucleus–cytoplasm cross‐talk in the aging brain. J Neurosci Res 2019; 98:247-261. [DOI: 10.1002/jnr.24446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 04/10/2019] [Accepted: 05/06/2019] [Indexed: 12/13/2022]
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Escobar-Henriques M, Joaquim M. Mitofusins: Disease Gatekeepers and Hubs in Mitochondrial Quality Control by E3 Ligases. Front Physiol 2019; 10:517. [PMID: 31156446 PMCID: PMC6533591 DOI: 10.3389/fphys.2019.00517] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 04/11/2019] [Indexed: 02/06/2023] Open
Abstract
Mitochondria are dynamic organelles engaged in quality control and aging processes. They constantly undergo fusion, fission, transport, and anchoring events, which empower mitochondria with a very interactive behavior. The membrane remodeling processes needed for fusion require conserved proteins named mitofusins, MFN1 and MFN2 in mammals and Fzo1 in yeast. They are the first determinants deciding on whether communication and content exchange between different mitochondrial populations should occur. Importantly, each cell possesses hundreds of mitochondria, with a different severity of mitochondrial mutations or dysfunctional proteins, which potentially spread damage to the entire network. Therefore, the degree of their merging capacity critically influences cellular fitness. In turn, the mitochondrial network rapidly and dramatically changes in response to metabolic and environmental cues. Notably, cancer or obesity conditions, and stress experienced by neurons and cardiomyocytes, for example, triggers the downregulation of mitofusins and thus fragmentation of mitochondria. This places mitofusins upfront in sensing and transmitting stress. In fact, mitofusins are almost entirely exposed to the cytoplasm, a topology suitable for a critical relay point in information exchange between mitochondria and their cellular environment. Consistent with their topology, mitofusins are either activated or repressed by cytosolic post-translational modifiers, mainly by ubiquitin. Ubiquitin is a ubiquitous small protein orchestrating multiple quality control pathways, which is covalently attached to lysine residues in its substrates, or in ubiquitin itself. Importantly, from a chain of events also mediated by E1 and E2 enzymes, E3 ligases perform the ultimate and determinant step in substrate choice. Here, we review the ubiquitin E3 ligases that modify mitofusins. Two mitochondrial E3 enzymes—March5 and MUL1—one ligase located to the ER—Gp78—and finally three cytosolic enzymes—MGRN1, HUWE1, and Parkin—were shown to ubiquitylate mitofusins, in response to a variety of cellular inputs. The respective outcomes on mitochondrial morphology, on contact sites to the endoplasmic reticulum and on destructive processes, like mitophagy or apoptosis, are presented. Ultimately, understanding the mechanisms by which E3 ligases and mitofusins sense and bi-directionally signal mitochondria-cytosolic dysfunctions could pave the way for therapeutic approaches in neurodegenerative, cardiovascular, and obesity-linked diseases.
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Affiliation(s)
- Mafalda Escobar-Henriques
- Center for Molecular Medicine Cologne (CMMC), Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Mariana Joaquim
- Center for Molecular Medicine Cologne (CMMC), Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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Gagnier L, Belancio VP, Mager DL. Mouse germ line mutations due to retrotransposon insertions. Mob DNA 2019; 10:15. [PMID: 31011371 PMCID: PMC6466679 DOI: 10.1186/s13100-019-0157-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/01/2019] [Indexed: 12/24/2022] Open
Abstract
Transposable element (TE) insertions are responsible for a significant fraction of spontaneous germ line mutations reported in inbred mouse strains. This major contribution of TEs to the mutational landscape in mouse contrasts with the situation in human, where their relative contribution as germ line insertional mutagens is much lower. In this focussed review, we provide comprehensive lists of TE-induced mouse mutations, discuss the different TE types involved in these insertional mutations and elaborate on particularly interesting cases. We also discuss differences and similarities between the mutational role of TEs in mice and humans.
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Affiliation(s)
- Liane Gagnier
- 1Terry Fox Laboratory, BC Cancer and Department of Medical Genetics, University of British Columbia, V5Z1L3, Vancouver, BC Canada
| | - Victoria P Belancio
- 2Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane Cancer Center, Tulane Center for Aging, New Orleans, LA 70112 USA
| | - Dixie L Mager
- 1Terry Fox Laboratory, BC Cancer and Department of Medical Genetics, University of British Columbia, V5Z1L3, Vancouver, BC Canada
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13
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Human melanocortin 1 receptor-mediated ubiquitination of nonvisual arrestins. Role of Mahogunin Ring Finger 1 E3 ligase. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:76-94. [DOI: 10.1016/j.bbamcr.2017.09.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 09/15/2017] [Accepted: 09/21/2017] [Indexed: 11/23/2022]
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14
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Pusapati GV, Kong JH, Patel BB, Krishnan A, Sagner A, Kinnebrew M, Briscoe J, Aravind L, Rohatgi R. CRISPR Screens Uncover Genes that Regulate Target Cell Sensitivity to the Morphogen Sonic Hedgehog. Dev Cell 2017; 44:113-129.e8. [PMID: 29290584 PMCID: PMC5792066 DOI: 10.1016/j.devcel.2017.12.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 11/20/2017] [Accepted: 12/01/2017] [Indexed: 12/21/2022]
Abstract
To uncover regulatory mechanisms in Hedgehog (Hh) signaling, we conducted genome-wide screens to identify positive and negative pathway components and validated top hits using multiple signaling and differentiation assays in two different cell types. Most positive regulators identified in our screens, including Rab34, Pdcl, and Tubd1, were involved in ciliary functions, confirming the central role for primary cilia in Hh signaling. Negative regulators identified included Megf8, Mgrn1, and an unannotated gene encoding a tetraspan protein we named Atthog. The function of these negative regulators converged on Smoothened (SMO), an oncoprotein that transduces the Hh signal across the membrane. In the absence of Atthog, SMO was stabilized at the cell surface and concentrated in the ciliary membrane, boosting cell sensitivity to the ligand Sonic Hedgehog (SHH) and consequently altering SHH-guided neural cell-fate decisions. Thus, we uncovered genes that modify the interpretation of morphogen signals by regulating protein-trafficking events in target cells.
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Affiliation(s)
- Ganesh V Pusapati
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Jennifer H Kong
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Bhaven B Patel
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Arunkumar Krishnan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Andreas Sagner
- The Francis Crick Institute, Midland Road, London NW1 1AT, UK
| | - Maia Kinnebrew
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - James Briscoe
- The Francis Crick Institute, Midland Road, London NW1 1AT, UK
| | - L Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Rajat Rohatgi
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
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15
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Sasamori S, Wiewel AS, Thomson VA, Kobayashi M, Nakata K, Suzuki H. Potential Causative Mutation for Melanism in Rats Identified in the Agouti Signaling Protein Gene (Asip) of the Rattus rattus Species Complex on Okinawa Island, Japan. Zoolog Sci 2017; 34:513-522. [PMID: 29219041 DOI: 10.2108/zs170027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The occurrence of black fur, or melanism, in many mammalian species is known to be linked to DNA sequence variation in the agouti signaling protein (Asip) gene, which is a major determinant of eumelanin and pheomelanin pigments in coat color. We investigated 38 agouti (i.e., banded wildtype) and four melanistic Rattus rattus species complex (RrC) lineage II specimens from Okinawa Island, Ryukyu Islands, Japan, for genetic variation in three exons and associated flanking regions in the Asip gene. On Okinawa, a predicted loss-of-function mutation caused by a cysteine to serine amino acid change at p.124C>S (c.370T>A) in the highly conserved functional domain of Asip was found in melanistic rats, but was absent in agouti specimens, suggesting that the p.124C>S mutation is responsible for the observed melanism. Phylogeographic analysis found that Asip sequences from Okinawan RrC lineage II, including both agouti and melanistic specimens, differed from: 1) both agouti and melanistic RrC lineage I from Otaru, Hokkaido, Japan, and 2) agouti RrC lineages I and II from South Australia. This suggests the possibility of in-situ mutation of the Asip gene, either within the RrC lineage II population on Okinawa or in an unsampled RrC lineage II population with biogeographic links to Okinawa, although incomplete lineage sorting could not be ruled out.
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Affiliation(s)
- Shoichi Sasamori
- 1 Division of Bioscience, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Andrew S Wiewel
- 2 School of Biological Sciences, University of Adelaide, North Terrace, Adelaide SA 5005, Australia
| | - Vicki A Thomson
- 2 School of Biological Sciences, University of Adelaide, North Terrace, Adelaide SA 5005, Australia
| | - Motoko Kobayashi
- 1 Division of Bioscience, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Katsushi Nakata
- 3 Yambaru Wildlife Conservation Center, Ministry of the Environment, Kunigami-son, Okinawa 905-1413, Japan
| | - Hitoshi Suzuki
- 1 Division of Bioscience, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan
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16
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Chronicle of a Neuronal Death Foretold: Preventing Aging by Keeping MGRN1 at the Nucleus. Mol Cell 2017; 66:301-303. [PMID: 28475865 DOI: 10.1016/j.molcel.2017.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In this issue of Molecular Cell, Benvegnù et al. (2017) report an unexpected phenomenon by which the E3 ligase mahogunin ring finger-1 (MGRN1) translocates to the nucleus in an age-dependent manner, revealing an intriguing mechanism that allows for an adaptive neuronal response to proteotoxic stress, often seen with aging.
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17
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Benvegnù S, Mateo MI, Palomer E, Jurado-Arjona J, Dotti CG. Aging Triggers Cytoplasmic Depletion and Nuclear Translocation of the E3 Ligase Mahogunin: A Function for Ubiquitin in Neuronal Survival. Mol Cell 2017; 66:358-372.e7. [DOI: 10.1016/j.molcel.2017.04.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 12/19/2016] [Accepted: 04/05/2017] [Indexed: 12/20/2022]
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18
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Herraiz C, Garcia-Borron JC, Jiménez-Cervantes C, Olivares C. MC1R signaling. Intracellular partners and pathophysiological implications. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2448-2461. [PMID: 28259754 DOI: 10.1016/j.bbadis.2017.02.027] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 01/11/2017] [Accepted: 02/23/2017] [Indexed: 12/12/2022]
Abstract
The melanocortin-1 receptor (MC1R) preferentially expressed in melanocytes is best known as a key regulator of the synthesis of epidermal melanin pigments. Its paracrine stimulation by keratinocyte-derived melanocortins also activates DNA repair pathways and antioxidant defenses to build a complex, multifaceted photoprotective response. Many MC1R actions rely on cAMP-dependent activation of two transcription factors, MITF and PGC1α, but pleiotropic MC1R signaling also involves activation of mitogen-activated kinases and AKT. MC1R partners such as β-arrestins, PTEN and the E3 ubiquitin ligase MGRN1 differentially regulate these pathways. The MC1R gene is complex and polymorphic, with frequent variants associated with skin phenotypes and increased cancer risk. We review current knowledge of signaling from canonical MC1R, its splice isoforms and natural polymorphic variants. Recently discovered intracellular targets and partners are also discussed, to highlight the diversity of mechanisms that may contribute to normal and pathological variation of pigmentation and sensitivity to solar radiation-induced damage. This article is part of a Special Issue entitled: Melanocortin Receptors - edited by Ya-Xiong Tao.
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Affiliation(s)
- Cecilia Herraiz
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and Instituto Murciano de Investigación Biosanitaria (IMIB), 30120 El Palmar, Murcia, Spain
| | - Jose C Garcia-Borron
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and Instituto Murciano de Investigación Biosanitaria (IMIB), 30120 El Palmar, Murcia, Spain.
| | - Celia Jiménez-Cervantes
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and Instituto Murciano de Investigación Biosanitaria (IMIB), 30120 El Palmar, Murcia, Spain
| | - Conchi Olivares
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and Instituto Murciano de Investigación Biosanitaria (IMIB), 30120 El Palmar, Murcia, Spain
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19
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Cheng D, Xiong C, Li J, Sui C, Wang S, Li H, Jiang X. The effect of mahogunin gene mutant on reproduction in male mice: a new sight for infertility? Andrologia 2012; 46:98-105. [PMID: 23210986 DOI: 10.1111/and.12050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2012] [Indexed: 01/29/2023] Open
Abstract
Mahogunin is an important mediator of chromogenesis and neurodegeneration. Mahoganoid is a mutation of the mahogunin gene, which causes a pleiotropic phenotype that includes suppression of obesity, spongiform neurodegeneration and improvement of insulin sensitivity. Our previous research found that mahoganoid widely expressed in the male rat reproductive system, and mahoganoid-deficient mice have reduced embryonic viability. But the reproductive change in mahogunin knockout (md(nc) ) male mice has not been reported previously. Here, we report that the mahogunin mRNA also widely exists in reproductive system of male mice, and its mRNA expression in the testis was in accordance with the first spermatogenesis wave cycle. Moreover, we find that md(nc) male mice were able to mate with females but no pups are delivered. Besides, the sperms' active progressive motility and hormone secretion (E2, FSH, LH, PRL) were obviously decreased while abnormal sperm rate showed no significant difference in md(nc) compared to wild-type (WT) male mice. This study indicates the mahogunin deficiency results in the infertility of male mice, disruption of hormones secretion and impaired active progressive motility, which may additionally illuminate the aetiology of male infertility in human.
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Affiliation(s)
- D Cheng
- Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Reproductive medical center, Renmin hospital of WuHan University, Wuhan, China
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20
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Abstract
Obesity promotes increased secretion of a number of inflammatory factors from adipose tissue. These factors include cytokines and very lately, extracellular matrix components (ECM). Biglycan, a small leucine rich proteoglycan ECM protein, is up-regulated in obesity and has recently been recognized as a pro-inflammatory molecule. However, it is unknown whether biglycan contributes to adipose tissue dysfunction. In the present study, we characterized biglycan expression in various adipose depots in wild-type mice fed a low fat diet (LFD) or obesity-inducing high fat diet (HFD). High fat feeding induced biglycan mRNA expression in multiple adipose depots. Adiponectin is an adipokine with anti-inflammatory and insulin sensitizing effects. Due to the importance of adiponectin, we examined the effect of biglycan on adiponectin expression. Comparison of adiponectin expression in biglycan knockout (bgn(-/0)) and wild-type (bgn(+/0)) reveals higher adiponectin mRNA and protein in epididymal white adipose tissue in bgn(-/0) mice, as well higher serum concentration of adiponectin, and lower serum insulin concentration. On the contrary, knockdown of biglycan in 3T3-L1 adipocytes led to decreased expression and secretion of adiponectin. Furthermore, treatment of 3T3-L1 adipocytes with conditioned medium from biglycan treated macrophages resulted in an increase in adiponectin mRNA expression. These data suggest a link between biglycan and adiponectin expression. However, the difference in the pattern of regulation between in vivo and in vitro settings reveals the complexity of this relationship.
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21
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Snyder EE, Walts B, Pérusse L, Chagnon YC, Weisnagel SJ, Rankinen T, Bouchard C. The Human Obesity Gene Map: The 2003 Update. ACTA ACUST UNITED AC 2012; 12:369-439. [PMID: 15044658 DOI: 10.1038/oby.2004.47] [Citation(s) in RCA: 207] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.
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Affiliation(s)
- Eric E Snyder
- Human Genomics Laboratory, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana 70808-4124, USA
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22
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Abstract
Mahogunin ring fnger-1(MGRN1) encodes an E3 ubiquitin ligase and is mutated in the mahoganoid mouse. The mahoganoid mouse mutant shows similarities to the phenotype of another spontaneous mouse mutation known as mahogunin (mutation in attractin) presenting with dark coat color, spongiform neurodegeneration, and high embryonic lethality. It has long been hypothesized that MGRN1 may down-regulate the function of the melanocortin 1 receptor (MC1R) via ubiquitination or internalization because it has been shown to possess E3 ubiquitin ligase activity. However, a recent study revealed that MGRN1's role in MC1R function was independent of receptor ubiquitination and that MGRN1 negatively regulated MC1R function by competing with Gαs for receptor binding. In this study we attempted to determine whether MGRN1 is involved in the function of the melanocortin 2 receptor (MC2R). We show that MGRN1 is expressed in the zona glomerulosa and fasciculata cells of the adrenal cortex, and in transfected human embryonic kidney 293 cells it colocalizes at the cell surface with the MC2R, and coimmunoprecipitates with the MC2R. However MGRN1 did not appear to influence the cAMP-signaling function of the MC2R. In the presence of MGRN1 the MC2R is ubiquitinated and, after ACTH stimulation, evidence of multi-monoubiquitination appears. It therefore seems probable that the role of MGRN1 in the adrenal relates to the trafficking and/or degradation of the MC2R.
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Affiliation(s)
- Sadani N Cooray
- Centre for Endocrinology, Barts & the London School of Medicine & Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, United Kingdom
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23
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Overton JD, Leibel RL. Mahoganoid and mahogany mutations rectify the obesity of the yellow mouse by effects on endosomal traffic of MC4R protein. J Biol Chem 2011; 286:18914-29. [PMID: 21460229 DOI: 10.1074/jbc.m111.224592] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ubiquitous overexpression of agouti-signaling protein (ASP), a paracrine-signaling molecule that regulates pigment-type switching in the hair follicle of the mouse, is responsible for the obesity and yellow pelage of the Yellow mouse (A(y)). Mahogany (Attractin, Atrn/mg) and mahoganoid (Mahogunin Ring Finger-1, Mgrn1/md) are mutations epistatic to A(y). These mutations have been described as suppressors of ASP action, blocking its antagonizing effects on the melanocortin 1 and 4 receptors (MC1R and MC4R) in the skin and the brain, respectively, via unknown mechanisms. Here, we describe the molecular bases for the md- and mg-dependent rescue of the A(y) phenotype at the MC4R. We show that overexpression of ASP inhibits the rise in cAMP levels in response to α-melanocyte-stimulating hormone, an MC4R agonist, by blocking ligand binding and by directing MC4R trafficking to the lysosome. Loss-of-function of either attractin or MGRN1 blocks ASP-dependent MC4R degradation and promotes increased trafficking of internalized MC4R to the cell surface, but it does not restore α-melanocyte-stimulating hormone-dependent cAMP signaling. We propose that MGRN1 and attractin are components of an evolutionarily conserved receptor trafficking pathway and that the md and mg mutations rescue the A(y) phenotypes by a primarily cAMP-independent mechanism promoting trafficking of MC4R and likely MC1R away from the lysosome toward the cell surface.
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Affiliation(s)
- John D Overton
- Division of Molecular Genetics, Department of Pediatrics, Naomi Berrie Diabetes Center and the Institute of Human Nutrition, Columbia University, New York, New York 10032, USA.
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Breit A, Büch TRH, Boekhoff I, Solinski HJ, Damm E, Gudermann T. Alternative G protein coupling and biased agonism: new insights into melanocortin-4 receptor signalling. Mol Cell Endocrinol 2011; 331:232-40. [PMID: 20674667 DOI: 10.1016/j.mce.2010.07.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Revised: 05/06/2010] [Accepted: 07/13/2010] [Indexed: 11/20/2022]
Abstract
The melanocortin-4 receptor (MC4R) is a prototypical G protein-coupled receptor (GPCR) that plays a considerable role in controlling appetite and energy homeostasis. Signalling initiated by MC4R is orchestrated by multiple agonists, inverse agonism and by interactions with accessory proteins. The exact molecular events translating MC4R signalling into its physiological role, however, are not fully understood. This review is an attempt to summarize new aspects of MC4R signalling in the context of its recently discovered alternative G protein coupling, and to give a perspective on how future research could improve our knowledge about the intertwining molecular mechanisms that are responsible for the regulation of energy homeostasis by the melanocortin system.
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Affiliation(s)
- Andreas Breit
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Goethestrasse 33, Ludwig-Maximilians-Universität München, 80336 München, Germany.
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25
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Beta-catenin activity in the dermal papilla of the hair follicle regulates pigment-type switching. Proc Natl Acad Sci U S A 2010; 107:21564-9. [PMID: 21098273 DOI: 10.1073/pnas.1007326107] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The switch between black and yellow pigment is mediated by the interaction between Melanocortin receptor 1 (Mc1r) and its antagonist Agouti, but the genetic and developmental mechanisms that modify this interaction to obtain different coat color in distinct environments are poorly understood. Here, the role of Wnt/β-catenin signaling in the regulation of pigment-type switching was studied. Loss and gain of function of β-catenin in the dermal papilla (DP) of the hair follicle results in yellow and black animals, respectively. β-Catenin activity in the DP suppresses Agouti expression and activates Corin, a negative regulator of Agouti activity. In addition, β-catenin activity in the DP regulates melanocyte activity by a mechanism that is independent of both Agouti and Corin. The coordinate and inverse regulation of Agouti and Corin renders pelage pigmentation sensitive to changes in β-catenin activity in the DP that do not alter pelage structure. As a result, the signals that specify two biologically distinct quantitative traits are partially uncoupled despite their common regulation by the β-catenin pathway in the same cells.
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Abstract
Neurons are highly specialized cells whose connectivity at synapses subserves rapid information transfer in the brain. Proper information processing, learning, and memory storage in the brain requires continuous remodeling of synaptic networks. Such remodeling includes synapse formation, elimination, synaptic protein turnover, and changes in synaptic transmission. An emergent mechanism for regulating synapse function is posttranslational modification through the ubiquitin pathway at the postsynaptic membrane. Here, we discuss recent findings implicating ubiquitination and protein degradation in postsynaptic function and plasticity. We describe postsynaptic ubiquitination pathways and their role in brain development, neuronal physiology, and brain disorders.
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Affiliation(s)
- Angela M Mabb
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Walker WP, Gunn TM. Shades of meaning: the pigment-type switching system as a tool for discovery. Pigment Cell Melanoma Res 2010; 23:485-95. [PMID: 20465596 DOI: 10.1111/j.1755-148x.2010.00721.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The pigment-type switching system, which controls whether melanocytes produce black/brown eumelanin or yellow/red pheomelanin, is responsible for many familiar coat coloration patterns in both domestic and wild mammals. In conjunction with the accessory proteins attractin and mahogunin ring finger 1, endogenous agonists and antagonists modulate signaling by the melanocortin 1 receptor to determine pigment type. Mutations in pigment-type switching genes can cause a variety of pleiotropic phenotypes, and these are often similar between mutants at different loci because the proteins encoded by these genes act together as part of conserved molecular pathways that are deployed in multiple biological contexts. When this is the case, pigment-type switching provides a powerful model system for elucidating the shared molecular mechanisms underlying the pigmentary and non-pigmentary phenotypes. This review outlines the current understanding of the pigment-type switching pathway and discusses the opportunities that exist for exploring the molecular basis of pleiotropic phenotypes using this model system.
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28
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Kumar KG, Sutton GM, Dong JZ, Roubert P, Plas P, Halem HA, Culler MD, Yang H, Dixit VD, Butler AA. Analysis of the therapeutic functions of novel melanocortin receptor agonists in MC3R- and MC4R-deficient C57BL/6J mice. Peptides 2009; 30:1892-900. [PMID: 19646498 PMCID: PMC2755620 DOI: 10.1016/j.peptides.2009.07.012] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 07/20/2009] [Accepted: 07/20/2009] [Indexed: 12/20/2022]
Abstract
Melanocortin receptor agonists act in the brain to regulate food intake and body weight and, independently of these actions, affect insulin sensitivity. These experiments investigated the function of novel non-selective melanocortin receptor agonists (BIM-22493, BIM-22511) that cross the blood-brain barrier when administered peripherally. Treatment of diet induced obese C57BL/6J (B6) mice with melanocortin agonists administered peripherally improved obesity, hyperinsulinemia (approximately 50%) and fatty liver disease. Specificity of function was determined using B6 melanocortin-3 and melanocortin-4 receptor knockout mice (MC3RKO, MC4RKO). Chow fed MC4RKO but not MC3RKO used for these tests exhibited obesity, hyperinsulinemia and severe hepatosteatosis associated with increased expression of insulin-stimulated genes involved in lipogenesis. Reduced food intake associated with acute BIM-22493 treatment, and weight loss associated with 14 days of treatment with BIM-22511, required functional MC4R but not MC3R. However, while 14 days of treatment with BIM-22511 did not affect body weight and even increased cumulative food intake in MC4RKO, a significant reduction (approximately 50%) in fasting insulin was still observed. Despite lowering insulin, chronic treatment with BIM-22511 did not improve hepatosteatosis in MC4RKO, and did not affect hepatic lipogenic gene expression. Together, these results demonstrate that peripherally administered melanocortin receptor agonists regulate body weight, liver metabolism and glucose homeostasis through independent pathways. MC4R are necessary for melanocortin agonist-induced weight loss and improvements in liver metabolism, but are not required for improvements in hyperinsulinemia. Agonists with activity at MC4R improve glucose homeostasis at least partially by causing weight loss, however other melanocortin receptors may have potential for treating aberrations in glucose homeostasis associated with obesity.
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MESH Headings
- Animals
- Diet
- Eating
- Energy Metabolism
- Female
- Glucose/metabolism
- Humans
- Liver/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Obesity/metabolism
- Receptor, Melanocortin, Type 3/agonists
- Receptor, Melanocortin, Type 3/genetics
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/metabolism
- Weight Loss
- alpha-MSH/analogs & derivatives
- alpha-MSH/pharmacology
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Affiliation(s)
- K. Ganesh Kumar
- Neuropeptides Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
| | - Gregory M. Sutton
- Neuropeptides Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
| | - Jesse Z. Dong
- Biomeasure Incorporated, IPSEN, Milford, MA 01757, USA
| | | | | | | | | | - Hyunwon Yang
- Laboratory of Neuroendocrine Immunology, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
| | - Vishwa D. Dixit
- Laboratory of Neuroendocrine Immunology, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
| | - Andrew A. Butler
- Neuropeptides Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
- Present address for correspondence and reprint requests: Andrew A. Butler, The Scripps Research Institute – Scripps Florida, 130 Scripps Way, Jupiter, FL 33458, Ph: 001 561 228 2957, Fax: 001 561 228 3059,
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Pérez-Oliva AB, Olivares C, Jiménez-Cervantes C, García-Borrón JC. Mahogunin ring finger-1 (MGRN1) E3 ubiquitin ligase inhibits signaling from melanocortin receptor by competition with Galphas. J Biol Chem 2009; 284:31714-25. [PMID: 19737927 DOI: 10.1074/jbc.m109.028100] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mahogunin ring finger-1 (MGRN1) is a RING domain-containing ubiquitin ligase mutated in mahoganoid, a mouse mutation causing coat color darkening, congenital heart defects, high embryonic lethality, and spongiform neurodegeneration. The melanocortin hormones regulate pigmentation, cortisol production, food intake, and body weight by signaling through five G protein-coupled receptors positively coupled to the cAMP pathway (MC1R-MC5R). Genetic analysis has shown that mouse Mgrn1 is an accessory protein for melanocortin signaling that may inhibit MC1R and MC4R by unknown mechanisms. These melanocortin receptors (MCRs) regulate pigmentation and body weight, respectively. We show that human melanoma cells express 4 MGRN1 isoforms differing in the C-terminal exon 17 and in usage of exon 12. This exon contains nuclear localization signals. MGRN1 isoforms decreased MC1R and MC4R signaling to cAMP, without effect on beta(2)-adrenergic receptor. Inhibition was independent on receptor plasma membrane expression, ubiquitylation, internalization, or stability and occurred upstream of Galpha(s) binding to/activation of adenylyl cyclase. MGRN1 co-immunoprecipitated with MCRs, suggesting a physical interaction of the proteins. Significantly, overexpression of Galpha(s) abolished the inhibitory effect of MGRN1 and decreased co-immunoprecipitation with MCRs, suggesting competition between MGRN1 and Galpha(s) for binding to MCRs. Although all MGRN1s were located in the cytosol in the absence of MCRs, exon 12-containing isoforms accumulated in the nuclei upon co-expression with the receptors. Therefore, MGRN1 inhibits MCR signaling by a new mechanism involving displacement of Galpha(s), thus accounting for key features of the mahoganoid phenotype. Moreover, MGRN1 might provide a novel pathway for melanocortin signaling from the cell surface to the nucleus.
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Affiliation(s)
- Ana B Pérez-Oliva
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia, 30100 Murcia, Spain
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Kingsley EP, Manceau M, Wiley CD, Hoekstra HE. Melanism in peromyscus is caused by independent mutations in agouti. PLoS One 2009; 4:e6435. [PMID: 19649329 PMCID: PMC2713407 DOI: 10.1371/journal.pone.0006435] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Accepted: 06/30/2009] [Indexed: 12/31/2022] Open
Abstract
Identifying the molecular basis of phenotypes that have evolved independently can provide insight into the ways genetic and developmental constraints influence the maintenance of phenotypic diversity. Melanic (darkly pigmented) phenotypes in mammals provide a potent system in which to study the genetic basis of naturally occurring mutant phenotypes because melanism occurs in many mammals, and the mammalian pigmentation pathway is well understood. Spontaneous alleles of a few key pigmentation loci are known to cause melanism in domestic or laboratory populations of mammals, but in natural populations, mutations at one gene, the melanocortin-1 receptor (Mc1r), have been implicated in the vast majority of cases, possibly due to its minimal pleiotropic effects. To investigate whether mutations in this or other genes cause melanism in the wild, we investigated the genetic basis of melanism in the rodent genus Peromyscus, in which melanic mice have been reported in several populations. We focused on two genes known to cause melanism in other taxa, Mc1r and its antagonist, the agouti signaling protein (Agouti). While variation in the Mc1r coding region does not correlate with melanism in any population, in a New Hampshire population, we find that a 125-kb deletion, which includes the upstream regulatory region and exons 1 and 2 of Agouti, results in a loss of Agouti expression and is perfectly associated with melanic color. In a second population from Alaska, we find that a premature stop codon in exon 3 of Agouti is associated with a similar melanic phenotype. These results show that melanism has evolved independently in these populations through mutations in the same gene, and suggest that melanism produced by mutations in genes other than Mc1r may be more common than previously thought.
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Affiliation(s)
- Evan P Kingsley
- Department of Organismic and Evolutionary Biology and the Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, United States of America.
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31
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Concepcion D, Flores-García L, Hamilton BA. Multipotent genetic suppression of retrotransposon-induced mutations by Nxf1 through fine-tuning of alternative splicing. PLoS Genet 2009; 5:e1000484. [PMID: 19436707 PMCID: PMC2674570 DOI: 10.1371/journal.pgen.1000484] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 04/17/2009] [Indexed: 11/18/2022] Open
Abstract
Cellular gene expression machinery has coevolved with molecular parasites, such as viruses and transposons, which rely on host cells for their expression and reproduction. We previously reported that a wild-derived allele of mouse Nxf1 (Tap), a key component of the host mRNA nuclear export machinery, suppresses two endogenous retrovirus-induced mutations and shows suggestive evidence of positive selection. Here we show that Nxf1CAST suppresses a specific and frequent class of intracisternal A particle (IAP)-induced mutations, including Ap3d1mh2J, a model for Hermansky-Pudlak syndrome, and Atcayhes, an orthologous gene model for Cayman ataxia, among others. The molecular phenotype of suppression includes ∼two-fold increase in the level of correctly-spliced mRNA and a decrease in mutant-specific, alternatively-processed RNA accumulating from the inserted allele. Insertional mutations involving ETn and LINE elements are not suppressed, demonstrating a high degree of specificity to this suppression mechanism. These results implicate Nxf1 in some instances of pre-mRNA processing, demonstrate the useful range of Nxf1CAST alleles for manipulating existing mouse models of disease, and specifically imply a low functional threshold for therapeutic benefit in Cayman ataxia. Retroviruses and transposable elements are molecular parasites that integrate into the host genome and require host cell machinery for gene expression, replication and dissemination. Integrating elements can alter the expression of nearby host genes through both transcriptional and post-transcriptional mechanisms. Components of the host cell machinery that can adapt to favor genetic programs of the host cell over those of the parasite may afford one level of innate immunity. In laboratory mice, endogenous retroviruses are virus-derived mobile elements that account for many spontaneous mutations. A frequent class involves retrotransposition into introns of genes in the transcriptional sense orientation, which alters host gene pre-mRNA splicing. Here we show that for the intracisternal A particle (IAP) family of endogenous retroviruses, an allele of the canonical mRNA export factor Nxf1 found in wild Asiatic mice (Mus musculus castaneus) suppresses most insertions of this class (six of seven tested). To our knowledge, these results make Nxf1 the most broadly interacting modifier gene yet documented in this well-studied species. These results have significant implications for manipulating gene expression in mouse models of disease, the role of Nxf1 in pre-mRNA processing and in the dynamic range for therapeutic intervention in Cayman ataxia.
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Affiliation(s)
- Dorothy Concepcion
- Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
- Department of Cellular and Molecular Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
- Rebecca and John Moores UCSD Cancer Center, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - Lisbeth Flores-García
- Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
- Department of Cellular and Molecular Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
- Rebecca and John Moores UCSD Cancer Center, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - Bruce A. Hamilton
- Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
- Department of Cellular and Molecular Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
- Rebecca and John Moores UCSD Cancer Center, University of California San Diego School of Medicine, La Jolla, California, United States of America
- * E-mail:
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32
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Herrero Hernández E. On the track of the white tiger: pigmentation could be linked to prion diseases, and location explains why. Med Hypotheses 2009; 73:309-11. [PMID: 19423237 DOI: 10.1016/j.mehy.2009.03.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 03/04/2009] [Accepted: 03/08/2009] [Indexed: 10/20/2022]
Abstract
Certain rodent pigmentation mutants spontaneously develop brain spongiform changes. It is hypothesized that animals, and possibly humans, characterized by certain pigmentation gene variants could be more susceptible to prion diseases, which are characterized by this type of neuropathology. This hypothesis could be explained by the common location of the prion protein and several important pigmentation genes in the same chromosome. This common location can promote the joint transfer of both pigmentary and prion protein genes to the progeny. Pigmentation genes could also play a role in regulating protein folding and aggregation. Understanding the relationship between pigmentation genes and prion genes could lead to identify pigmentation variants at higher risk of prion diseases and understand the etiopathogenesis of these still invariably lethal disorders.
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Affiliation(s)
- Elena Herrero Hernández
- Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Mail Code L-606, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA.
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Fernandez LP, Milne RL, Pita G, Floristan U, Sendagorta E, Feito M, Avilés JA, Martin-Gonzalez M, Lázaro P, Benítez J, Ribas G. Pigmentation-related genes and their implication in malignant melanoma susceptibility. Exp Dermatol 2009; 18:634-42. [PMID: 19320733 DOI: 10.1111/j.1600-0625.2009.00846.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human pigmentation appears to be one of the main modulators of individual risk of developing malignant melanoma (MM). A large number of genes are known to be involved in rare pigmentary disorders and explain most of the variation in pigmentation phenotypes seen in human populations. This Spanish case-control study included 205 patients with melanoma and 245 control subjects. Thirty-one single nucleotide polymorphisms (SNPs) in genes that had been mainly associated with congenital pigmentation syndromes (ADTB3A, ATRN, CHS1, EDNRB, HPS, KIT, MGRN1, MITF, MLANA, MYO5A, MYO7A, OA1, OCA2, PAX3 and SOX10) were selected. We found that the variant allele of OCA2 R419Q (rs1800407) was associated with increased risk of MM (OR 1.55, 95% CI 1.04-2.31, P = 0.03). This effect on melanoma risk appeared to be stronger among individuals with solar lentigines, or at least 50 nevi. We also describe, for the first time, an association with the variant S1666C (rs2276288) in the MYO7A gene (OR 1.35; 95% CI 1.04-1.76; P = 0.03). Again, this association appeared to be stronger in several phenotypic groups such as individuals with fair skin and those with childhood sunburns. We also found that several variants in the pigmentation genes considered were associated with intermediate phenotypic characteristics. Our findings highlight the potential importance of pigmentation genes in sporadic MM susceptibility.
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Affiliation(s)
- Lara P Fernandez
- Human Genetics Group, Human Cancer Genetics Program, Spanish National Cancer Research Centre, Madrid E-28029, Spain
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Nomi M, Shimizu K. Establishment of consomic mice to clarify host susceptibility to caries. PEDIATRIC DENTAL JOURNAL 2009. [DOI: 10.1016/s0917-2394(09)70156-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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35
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The ubiquitin-proteasome system in spongiform degenerative disorders. Biochim Biophys Acta Mol Basis Dis 2008; 1782:700-12. [PMID: 18790052 PMCID: PMC2612938 DOI: 10.1016/j.bbadis.2008.08.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 08/13/2008] [Accepted: 08/15/2008] [Indexed: 12/20/2022]
Abstract
Spongiform degeneration is characterized by vacuolation in nervous tissue accompanied by neuronal death and gliosis. Although spongiform degeneration is a hallmark of prion diseases, this pathology is also present in the brains of patients suffering from Alzheimer’s disease, diffuse Lewy body disease, human immunodeficiency virus (HIV) infection, and Canavan’s spongiform leukodystrophy. The shared outcome of spongiform degeneration in these diverse diseases suggests that common cellular mechanisms must underlie the processes of spongiform change and neurodegeneration in the central nervous system. Immunohistochemical analysis of brain tissues reveals increased ubiquitin immunoreactivity in and around areas of spongiform change, suggesting the involvement of ubiquitin–proteasome system dysfunction in the pathogenesis of spongiform neurodegeneration. The link between aberrant ubiquitination and spongiform neurodegeneration has been strengthened by the discovery that a null mutation in the E3 ubiquitin–protein ligase mahogunin ring finger-1 (Mgrn1) causes an autosomal recessively inherited form of spongiform neurodegeneration in animals. Recent studies have begun to suggest that abnormal ubiquitination may alter intracellular signaling and cell functions via proteasome-dependent and proteasome-independent mechanisms, leading to spongiform degeneration and neuronal cell death. Further elucidation of the pathogenic pathways involved in spongiform neurodegeneration should facilitate the development of novel rational therapies for treating prion diseases, HIV infection, and other spongiform degenerative disorders.
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36
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Dokmanovic-Chouinard M, Chung WK, Chevre JC, Watson E, Yonan J, Wiegand B, Bromberg Y, Wakae N, Wright CV, Overton J, Ghosh S, Sathe GM, Ammala CE, Brown KK, Ito R, LeDuc C, Solomon K, Fischer SG, Leibel RL. Positional cloning of "Lisch-Like", a candidate modifier of susceptibility to type 2 diabetes in mice. PLoS Genet 2008; 4:e1000137. [PMID: 18654634 PMCID: PMC2464733 DOI: 10.1371/journal.pgen.1000137] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 06/20/2008] [Indexed: 12/17/2022] Open
Abstract
In 404 Lepob/ob F2 progeny of a C57BL/6J (B6) x DBA/2J (DBA) intercross, we mapped a DBA-related quantitative trait locus (QTL) to distal Chr1 at 169.6 Mb, centered about D1Mit110, for diabetes-related phenotypes that included blood glucose, HbA1c, and pancreatic islet histology. The interval was refined to 1.8 Mb in a series of B6.DBA congenic/subcongenic lines also segregating for Lepob. The phenotypes of B6.DBA congenic mice include reduced β-cell replication rates accompanied by reduced β-cell mass, reduced insulin/glucose ratio in blood, reduced glucose tolerance, and persistent mild hypoinsulinemic hyperglycemia. Nucleotide sequence and expression analysis of 14 genes in this interval identified a predicted gene that we have designated “Lisch-like” (Ll) as the most likely candidate. The gene spans 62.7 kb on Chr1qH2.3, encoding a 10-exon, 646–amino acid polypeptide, homologous to Lsr on Chr7qB1 and to Ildr1 on Chr16qB3. The largest isoform of Ll is predicted to be a transmembrane molecule with an immunoglobulin-like extracellular domain and a serine/threonine-rich intracellular domain that contains a 14-3-3 binding domain. Morpholino knockdown of the zebrafish paralog of Ll resulted in a generalized delay in endodermal development in the gut region and dispersion of insulin-positive cells. Mice segregating for an ENU-induced null allele of Ll have phenotypes comparable to the B.D congenic lines. The human ortholog, C1orf32, is in the middle of a 30-Mb region of Chr1q23-25 that has been repeatedly associated with type 2 diabetes. Type 2 diabetes (T2D) accounts for over 90% of instances of diabetes and is a leading cause of medical morbidity and mortality. Twin studies indicate a strong polygenic contribution to susceptibility within the context of obesity. Although approximately ten genes making important contributions to individual risk have been identified, it is clear that others remain to be identified. In this study, we intercrossed obese, diabetes-resistant and diabetes-prone mouse strains to implicate a genetic interval on mouse Chr1 associated with reduced β-cell numbers and elevated blood glucose. We narrowed the region using molecular genetics and computational approaches to identify a novel gene we designated “Lisch-like” (Ll). The orthologous human genetic interval has been repeatedly implicated in T2D. Mice with an induced mutation that reduces Ll expression are impaired in both β-cell development and glucose metabolism, and reduced expression of the homologous gene in zebrafish disrupts islet development. Ll is expressed in organs implicated in the pathophysiology of T2D (hypothalamus, islets, liver, and skeletal muscle) and is predicted to encode a transmembrane protein that could mediate cholesterol transport and/or convey signals related to cell division. Either mechanism could mediate effects on β-cell mass that would predispose to T2D.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Blood Glucose/genetics
- Chromosomes, Mammalian
- Cloning, Molecular
- Crosses, Genetic
- Diabetes Mellitus, Experimental/genetics
- Diabetes Mellitus, Type 2/genetics
- Genetic Predisposition to Disease
- Glucose Tolerance Test/methods
- Haplotypes
- Homozygote
- Insulin/blood
- Male
- Mice
- Mice, Congenic
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Obese
- Molecular Sequence Data
- Mutation
- Protein Isoforms/chemistry
- Protein Isoforms/genetics
- Quantitative Trait Loci
- Receptors, Cell Surface/genetics
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Affiliation(s)
| | - Wendy K. Chung
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Jean-Claude Chevre
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Elizabeth Watson
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Jason Yonan
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Beebe Wiegand
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Yana Bromberg
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Nao Wakae
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Chris V. Wright
- Vanderbilt University, Nashville, Tennessee, United States of America
| | - John Overton
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Sujoy Ghosh
- Clinical Pharmacology and Discovery Medicine, GlaxoSmithKline, Research Triangle Park, North Carolina, United States of America
| | - Ganesh M. Sathe
- Discovery Technology Group, GlaxoSmithKline Pharmaceuticals, Collegeville, Pennsylvania, United States of America
| | - Carina E. Ammala
- Center of Excellence for Drug Discovery, GlaxoSmithKline, Research Triangle Park, North Carolina, United States of America
| | - Kathleen K. Brown
- Center of Excellence for Drug Discovery, GlaxoSmithKline, Research Triangle Park, North Carolina, United States of America
| | - Rokuro Ito
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Charles LeDuc
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Keely Solomon
- Vanderbilt University, Nashville, Tennessee, United States of America
| | - Stuart G. Fischer
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
| | - Rudolph L. Leibel
- Naomi Berrie Diabetes Center, Columbia University, New York, New York, United States of America
- * E-mail:
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Enshell-Seijffers D, Lindon C, Morgan BA. The serine protease Corin is a novel modifier of the Agouti pathway. Development 2007; 135:217-25. [PMID: 18057101 DOI: 10.1242/dev.011031] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The hair follicle is a model system for studying epithelial-mesenchymal interactions during organogenesis. Although analysis of the epithelial contribution to these interactions has progressed rapidly, the lack of tools to manipulate gene expression in the mesenchymal component, the dermal papilla, has hampered progress towards understanding the contribution of these cells. In this work, Corin was identified in a screen to detect genes specifically expressed in the dermal papilla. It is expressed in the dermal papilla of all pelage hair follicle types from the earliest stages of their formation, but is not expressed elsewhere in the skin. Mutation of the Corin gene reveals that it is not required for morphogenesis of the hair follicle. However, analysis of the ;dirty blonde' phenotype of these mice reveals that the transmembrane protease encoded by Corin plays a critical role in specifying coat color and acts downstream of agouti gene expression as a suppressor of the agouti pathway.
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Affiliation(s)
- David Enshell-Seijffers
- Cutaneous Biology Research Center, Harvard Medical School and Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129, USA
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38
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Cota CD, Bagher P, Pelc P, Smith CO, Bodner CR, Gunn TM. Mice with mutations in Mahogunin ring finger-1 (Mgrn1) exhibit abnormal patterning of the left-right axis. Dev Dyn 2007; 235:3438-47. [PMID: 17075880 DOI: 10.1002/dvdy.20992] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Mahogunin Ring Finger 1 (Mgrn1) encodes a RING-containing protein with ubiquitin ligase activity that has been implicated in pigment-type switching. In addition to having dark fur, mice lacking MGRN1 develop adult-onset spongy degeneration of the central nervous system and have reduced embryonic viability. Observation of complete situs inversus in a small proportion of adult Mgrn1 mutant mice suggested that embryonic lethality resulted from congenital heart defects due to defective establishment and/or maintenance of the left-right (LR) axis. Here we report that Mgrn1 is expressed in a pattern consistent with a role in LR patterning during early development and that many Mgrn1 mutant embryos show abnormal expression of asymmetrically expressed genes involved in LR patterning. A range of complex heart defects was observed in 20-25% of mid-to-late gestation Mgrn1 mutant embryos and another 20% were dead. This finding was consistent with 46-60% mortality of mutants by weaning age. Our results indicate that Mgrn1 acts early in the LR signaling cascade and is likely to provide new insight into this developmental process as Nodal expression was uncoupled from expression of other Nodal-responsive genes in Mgrn1 mutant embryos. Our work identifies a novel role for MGRN1 in embryonic patterning and suggests that the ubiquitination of MGRN1 target genes is essential for the proper establishment and/or maintenance of the LR axis.
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Affiliation(s)
- Christina D Cota
- Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853, USA
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39
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Kim BY, Olzmann JA, Barsh GS, Chin LS, Li L. Spongiform neurodegeneration-associated E3 ligase Mahogunin ubiquitylates TSG101 and regulates endosomal trafficking. Mol Biol Cell 2007; 18:1129-42. [PMID: 17229889 PMCID: PMC1838976 DOI: 10.1091/mbc.e06-09-0787] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A null mutation in the gene encoding the putative E3 ubiquitin-protein ligase Mahogunin causes spongiform neurodegeneration, a recessively transmitted prion-like disease in mice. However, no substrates of Mahogunin have been identified, and the cellular role of Mahogunin is unknown. Here, we report the identification of TSG101, a key component of the endosomal sorting complex required for transport (ESCRT)-I, as a specific Mahogunin substrate. We find that Mahogunin interacts with the ubiquitin E2 variant (UEV) domain of TSG101 via its PSAP motif and that it catalyzes monoubiquitylation of TSG101 both in vivo and in vitro. Depletion of Mahogunin by small interfering RNAs in mammalian cells disrupts endosome-to-lysosome trafficking of epidermal growth factor receptor, resulting in prolonged activation of a downstream signaling cascade. Our findings support a role for Mahogunin in a proteasome-independent ubiquitylation pathway and suggest a link between dysregulation of endosomal trafficking and spongiform neurodegeneration.
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Affiliation(s)
- Bong Yoon Kim
- *Department of Pharmacology, Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322; and
| | - James A. Olzmann
- *Department of Pharmacology, Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322; and
| | - Gregory S. Barsh
- Department of Genetics and Pediatrics, Stanford University School of Medicine, Stanford, CA 94305
| | - Lih-Shen Chin
- *Department of Pharmacology, Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322; and
| | - Lian Li
- *Department of Pharmacology, Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322; and
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40
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Abstract
Avy/agouti (Avy) mice have late onset obesity related to overexpression of agouti signaling protein (ASP) in the hypothalamus. As mahogany modulates the actions of ASP, we tested the transport of mahogany peptide across the blood-brain barrier (BBB). The brain uptake of mahogany peptide was significantly higher in young Avy mice, and it preceded the surge of fat mass quantified by nuclear magnetic resonance. The results suggest a role of accelerated BBB transport in the epigenetics of Avy mice.
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Affiliation(s)
- W Pan
- Blood-Brain Barrier Lab, Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA.
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41
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Azouz A, Gunn TM, Duke-Cohan JS. Juvenile-onset loss of lipid-raft domains in attractin-deficient mice. Exp Cell Res 2006; 313:761-71. [PMID: 17196964 DOI: 10.1016/j.yexcr.2006.11.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 11/09/2006] [Accepted: 11/27/2006] [Indexed: 11/29/2022]
Abstract
Mutations at the attractin (Atrn) locus in mice result in altered pigmentation on an agouti background, higher basal metabolic rate and juvenile-onset hypomyelination leading to neurodegeneration, while studies on human immune cells indicate a chemotaxis regulatory function. The underlying biochemical defect remains elusive. In this report we identify a role for attractin in plasma membrane maintenance. In attractin's absence there is a decline in plasma membrane glycolipid-enriched rafts from normal levels at 8 weeks to a complete absence by 24 weeks. The structural integrity of lipid rafts depends upon cholesterol and sphingomyelin, and can be identified by partitioning within of ganglioside GM(1). Despite a significant fall in cellular cholesterol with maturity, and a lesser fall in both membrane and total cellular GM(1), these parameters lag behind raft loss, and are normal when hypomyelination/neurodegeneration has already begun thus supporting consequence rather than cause. These findings can be recapitulated in Atrn-deficient cell lines propagated in vitro. Further, signal transduction through complex membrane receptor assemblies is not grossly disturbed despite the complete absence of lipid rafts. We find these results compatible with a role for attractin in plasma membrane maintenance and consistent with the proposal that the juvenile-onset hypomyelination and neurodegeneration represent a defect in attractin-mediated raft-dependent myelin biogenesis.
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Affiliation(s)
- Abdallah Azouz
- Department of Medical Oncology, Dana-Farber Cancer Institute, and Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
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42
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Abstract
The melanocortin system refers to a set of hormonal, neuropeptidergic, and paracrine signaling pathways that are defined by components that include the five G protein-coupled melanocortin receptors; peptide agonists derived from the proopiomelanocortin preprohormone precursor; and the endogenous antagonists, agouti and agouti-related protein. This signaling system regulates a remarkably diverse array of physiological functions including pigmentation, adrenocortical steroidogenesis, energy homeostasis, natriuresis, erectile responses, energy homeostasis, and exocrine gland secretion. There are many complex and unique aspects of melanocortin signaling, such as the existence of endogenous antagonists, the agouti proteins, that act at three of the five melanocortin receptors. However, there is an aspect of melanocortin signaling that has facilitated highly reductionist approaches aimed at understanding the physiological functions of each receptor and peptide: in contrast to many peptides, the melanocortin agonists and antagonists are expressed in a limited number of very discrete locations. Similarly, the melanocortin receptors are also expressed in a limited number of discrete locations where they tend to be involved in rather circumscribed physiological functions. This review examines my laboratory's participation in the cloning of the melanocortin receptors and characterization of their physiological roles.
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Affiliation(s)
- Roger D Cone
- Center for the Study of Weight Regulation and Associated Disorders, and Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239-3098, USA.
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Phan LK, Chung WK, Leibel RL. The mahoganoid mutation (Mgrn1md) improves insulin sensitivity in mice with mutations in the melanocortin signaling pathway independently of effects on adiposity. Am J Physiol Endocrinol Metab 2006; 291:E611-20. [PMID: 16638826 DOI: 10.1152/ajpendo.00034.2006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mahoganoid (Mgrn1(md)) is a mutation of the mahogunin (Mgrn1) gene. The hypomorphic allele suppresses the yellow pigmentation and obesity of the A(y) mouse that ubiquitously overexpresses agouti signaling protein (ASP). To assess the physiological effects of MGRN1 on energy and glucose homeostasis, we generated animals doubly mutant for Mgrn1(md) and A(y), Lep(ob), or a null allele of Mc4r, and diet-induced obesity (DIO) mice segregating for Mgrn1(md). Mgrn1(md) suppressed the obesity, hyperglycemia, and hyperinsulinemia of A(y) mice. Mgrn1(md) suppressed A(y)-induced obesity by reducing food intake, and reduced adiposity in Lep(ob)/Lep(ob) females, but did not alter the body weight or body composition of mice fed a high-fat diet. There was no effect of Mgrn1(md) on weight gain, body composition, energy intake, or energy expenditure in Mc4r-null animals. Mgrn1(md) reduced circulating insulin concentrations in DIO, A(y), and Mc4r-null but not Lep(ob)/Lep(ob) mice. The effect of Mgrn1(md) on circulating insulin concentrations was not due primarily to reductions in fat mass, since the plasma insulin concentrations of Mgrn1(md) mice segregating for either A(y) or Mc4r-null alleles, adjusted for fat mass and plasma glucose, were reduced compared with A(y) and Mc4r mice, respectively. The effect of Mgrn1(md) on insulin sensitivity of Mc4r-null mice suggests that Mgrn1(md) may be increasing insulin sensitivity via the hypothalamic melanocortin-3 receptor pathway.
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MESH Headings
- Adiposity/genetics
- Adiposity/physiology
- Agouti Signaling Protein
- Animals
- Blood Glucose/metabolism
- Body Weight/physiology
- Eating/physiology
- Female
- Genotype
- Insulin/blood
- Insulin Resistance/physiology
- Intercellular Signaling Peptides and Proteins/genetics
- Leptin/blood
- Leptin/genetics
- Male
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Inbred Strains
- Mice, Knockout
- Mice, Mutant Strains
- Mice, Obese
- Mutation/genetics
- Obesity/etiology
- Obesity/genetics
- Obesity/physiopathology
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Ubiquitin-Protein Ligases/genetics
- Ubiquitin-Protein Ligases/physiology
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Affiliation(s)
- Loan K Phan
- Department of Pediatrics, Columbia University, New York, NY, USA
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Berryere TG, Kerns JA, Barsh GS, Schmutz SM. Association of an Agouti allele with fawn or sable coat color in domestic dogs. Mamm Genome 2005; 16:262-72. [PMID: 15965787 DOI: 10.1007/s00335-004-2445-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2004] [Accepted: 01/12/2005] [Indexed: 10/25/2022]
Abstract
The type of pigment synthesized in mammalian hair, yellow-red pheomelanin or black-brown eumelanin, depends on the interaction between Agouti protein and the Melanocortin 1 receptor. Although the genetics of pigmentation is broadly conserved across most mammalian species, pigment type-switching in domestic dogs is unusual because a yellow-tan coat with variable amounts of dark hair is thought to be caused by an allele of the Agouti locus referred to as fawn or sable (a(y)). In a large survey covering thirty seven breeds, we identified an Agouti allele with two missense alterations, A82S and R83H, which was present (heterozygous or homozygous) in 41 dogs (22 breeds) with a fawn or sable coat, but was absent from 16 dogs (8 breeds) with a black-and-tan or tricolor phenotype. In an additional 33 dogs (14 breeds) with a eumelanic coat, 8 (German Shepherd Dogs, Groenendaels, Schipperkes, or Shetland Sheepdogs) were homozygous for a previously reported mutation, non-agouti R96C; the remainder are likely to have carried dominant black, which is independent of and epistatic to Agouti. This work resolves some of the complexity in dog coat color genetics and provides diagnostic opportunities and practical guidelines for breeders.
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Affiliation(s)
- Tom G Berryere
- Department of Animal and Poultry Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8
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45
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Slominski A, Tobin DJ, Shibahara S, Wortsman J. Melanin pigmentation in mammalian skin and its hormonal regulation. Physiol Rev 2004; 84:1155-228. [PMID: 15383650 DOI: 10.1152/physrev.00044.2003] [Citation(s) in RCA: 1340] [Impact Index Per Article: 67.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cutaneous melanin pigment plays a critical role in camouflage, mimicry, social communication, and protection against harmful effects of solar radiation. Melanogenesis is under complex regulatory control by multiple agents interacting via pathways activated by receptor-dependent and -independent mechanisms, in hormonal, auto-, para-, or intracrine fashion. Because of the multidirectional nature and heterogeneous character of the melanogenesis modifying agents, its controlling factors are not organized into simple linear sequences, but they interphase instead in a multidimensional network, with extensive functional overlapping with connections arranged both in series and in parallel. The most important positive regulator of melanogenesis is the MC1 receptor with its ligands melanocortins and ACTH, whereas among the negative regulators agouti protein stands out, determining intensity of melanogenesis and also the type of melanin synthesized. Within the context of the skin as a stress organ, melanogenic activity serves as a unique molecular sensor and transducer of noxious signals and as regulator of local homeostasis. In keeping with these multiple roles, melanogenesis is controlled by a highly structured system, active since early embryogenesis and capable of superselective functional regulation that may reach down to the cellular level represented by single melanocytes. Indeed, the significance of melanogenesis extends beyond the mere assignment of a color trait.
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Affiliation(s)
- Andrzej Slominski
- Dept. of Pathology, Suite 599, University of Tennessee Health Science Center, 930 Madison Avenue, Memphis, TN 38163, USA.
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Holder JR, Haskell-Luevano C. Melanocortin ligands: 30 years of structure-activity relationship (SAR) studies. Med Res Rev 2004; 24:325-56. [PMID: 14994367 DOI: 10.1002/med.10064] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The challenge of peptide and peptidomimetic research is the development of methods and techniques to improve the biological properties of native peptides and to convert peptide ligands into non-peptide compounds. Improved biological properties of peptides includes enhancement of stability, potency, and receptor selectivity, for both in vivo and in vitro applications. The design of a ligand with specific activity and desired biological properties is a complex task, and, to accomplish this objective, knowledge about putative interactions between a ligand and the corresponding receptor will be valuable. This includes interactions for both the binding and signal transduction processes. Structure-activity relationship (SAR) studies involve systematic modification of a lead peptide and are designed to provide insight into potential interactions involved in the formation of the ligand-receptor complex. It is desirable to have knowledge about both favorable and unfavorable processes that may occur in putative ligand-receptor interactions that result in either receptor stimulation or inhibition. Herein, we discuss various SAR studies that have involved melanocortin peptides over three decades and the information these studies have provided to the melanocortin field.
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Affiliation(s)
- Jerry Ryan Holder
- Department of Medicinal Chemistry, University of Florida, Gainesville, Florida 32610, USA
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He L, Eldridge AG, Jackson PK, Gunn TM, Barsh GS. Accessory proteins for melanocortin signaling: attractin and mahogunin. Ann N Y Acad Sci 2003; 994:288-98. [PMID: 12851328 DOI: 10.1111/j.1749-6632.2003.tb03192.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Switching from eumelanin to pheomelanin synthesis during hair growth is accomplished by transient synthesis of Agouti protein, an inverse agonist for the melanocortin-1 receptor (Mc1r). The coat color mutations mahogany and mahoganoid prevent hair follicle melanocytes from responding to Agouti protein. The gene mutated in mahogany, which is also known as Attractin (Atrn), encodes a type I transmembrane protein that functions as an accessory receptor for Agouti protein. We have recently determined that the gene mutated in mahoganoid, which is also known as Mahogunin (Mgrn1), encodes an E3 ubiquitin ligase. Like Attractin, Mahogunin is conserved in invertebrate genomes, and its absence causes a pleiotropic phenotype that includes spongiform neurodegeneration.
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Affiliation(s)
- Lin He
- Departments of Pediatrics and Genetics and the Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA
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48
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Abstract
Previously we found elevated beacon gene expression in the hypothalamus of obese Psammomys obesus. Beacon administration into the lateral ventricle of P. obesus stimulated food intake and body weight gain. In the current study we used yeast two-hybrid technology to screen for proteins in the human brain that interact with beacon. CLK4, an isoform of cdc2/cdc28-like kinase family of proteins, was identified as a strong interacting partner for beacon. Using active recombinant proteins and a surface plasmon resonance based detection technique, we demonstrated that the three members of this subfamily of kinases (CLK1, 2, and 4) all interact with beacon. Based on the known sequence and functional properties of beacon and CLKs, we speculate that beacon could either modulate the function of key regulatory molecules such as PTP1B or control the expression patterns of specific genes involved in the central regulation of energy metabolism.
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49
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He L, Lu XY, Jolly AF, Eldridge AG, Watson SJ, Jackson PK, Barsh GS, Gunn TM. Spongiform degeneration in mahoganoid mutant mice. Science 2003; 299:710-2. [PMID: 12560552 DOI: 10.1126/science.1079694] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
mahoganoid is a mouse coat-color mutation whose pigmentary phenotype and genetic interactions resemble those of Attractin (Atrn). Atrn mutations also cause spongiform neurodegeneration. Here, we show that a null mutation for mahoganoid causes a similar age-dependent neuropathology that includes many features of prion diseases but without accumulation of protease-resistant prion protein. The gene mutated in mahoganoid encodes a RING-containing protein with E3 ubiquitin ligase activity in vitro. Similarities in phenotype, expression, and genetic interactions suggest that mahoganoid and Atrn genes are part of a conserved pathway for regulated protein turnover whose function is essential for neuronal viability.
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Affiliation(s)
- Lin He
- Department of Pediatrics, Department of Genetics, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
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