1
|
Multiple variants of the human presequence translocase motor subunit Magmas govern the mitochondrial import. J Biol Chem 2021; 297:101349. [PMID: 34715125 PMCID: PMC8605242 DOI: 10.1016/j.jbc.2021.101349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 10/16/2021] [Accepted: 10/22/2021] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial protein translocation is an intricately regulated process that requires dedicated translocases at the outer and inner membranes. The presequence translocase complex, translocase of the inner membrane 23, facilitates most of the import of preproteins containing presequences into the mitochondria, and its primary structural organization is highly conserved. As part of the translocase motor, two J-proteins, DnaJC15 and DnaJC19, are recruited to form two independent translocation machineries (translocase A and translocase B, respectively). On the other hand, the J-like protein subunit of translocase of the inner membrane 23, Mitochondria-associated granulocyte-macrophage colony-stimulating factor signaling molecule (Magmas) (orthologous to the yeast subunit Pam16), can regulate human import-motor activity by forming a heterodimer with DnaJC19 and DnaJC15. However, the precise coordinated regulation of two human import motors by a single Magmas protein is poorly understood. Here, we report two additional Magmas variants (Magmas-1 and Magmas-2) constitutively expressed in the mammalian system. Both the Magmas variants are functional orthologs of Pam16 with an evolutionarily conserved J-like domain critical for cell survival. Moreover, the Magmas variants are peripherally associated with the inner membrane as part of the human import motor for translocation. Our results demonstrate that Magmas-1 is predominantly recruited to translocase B, whereas Magmas-2 is majorly associated with translocase A. Strikingly, both the variants exhibit differential J-protein inhibitory activity in modulating import motor, thereby regulating overall translocase function. Based on our findings, we hypothesize that additional Magmas variants are of evolutionary significance in humans to maximize protein import in familial-linked pathological conditions.
Collapse
|
2
|
Ovarian Cancer, Cancer Stem Cells and Current Treatment Strategies: A Potential Role of Magmas in the Current Treatment Methods. Cells 2020; 9:cells9030719. [PMID: 32183385 PMCID: PMC7140629 DOI: 10.3390/cells9030719] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 03/01/2020] [Accepted: 03/06/2020] [Indexed: 12/18/2022] Open
Abstract
Epithelial ovarian cancer (EOC) constitutes 90% of ovarian cancers (OC) and is the eighth most common cause of cancer-related death in women. The cancer histologically and genetically is very complex having a high degree of tumour heterogeneity. The pathogenic variability in OC causes significant impediments in effectively treating patients, resulting in a dismal prognosis. Disease progression is predominantly influenced by the peritoneal tumour microenvironment rather than properties of the tumor and is the major contributor to prognosis. Standard treatment of OC patients consists of debulking surgery, followed by chemotherapy, which in most cases end in recurrent chemoresistant disease. This review discusses the different origins of high-grade serous ovarian cancer (HGSOC), the major sub-type of EOC. Tumour heterogeneity, genetic/epigenetic changes, and cancer stem cells (CSC) in facilitating HGSOC progression and their contribution in the circumvention of therapy treatments are included. Several new treatment strategies are discussed including our preliminary proof of concept study describing the role of mitochondria-associated granulocyte macrophage colony-stimulating factor signaling protein (Magmas) in HGSOC and its unique potential role in chemotherapy-resistant disease.
Collapse
|
3
|
Di K, Lomeli N, Bota DA, Das BC. Magmas inhibition as a potential treatment strategy in malignant glioma. J Neurooncol 2018; 141:267-276. [PMID: 30414099 DOI: 10.1007/s11060-018-03040-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 10/29/2018] [Indexed: 11/30/2022]
Abstract
PURPOSE Magmas (mitochondria-associated protein involved in granulocyte-macrophage colony-stimulating factor signal transduction) is a nuclear gene that encodes the mitochondrial import inner membrane translocase subunit Tim16. Magmas is highly conserved, ubiquitously expressed in mammalian cells, and is essential for cell viability. Magmas expression levels are increased in prostate cancers and pituitary adenomas. Moreover, silencing Magmas by RNAi sensitizes pituitary adenoma cells to pro-apoptotic stimuli and induces a G0/G1 accumulation. The aim of this study was to examine whether inhibition of Magmas by small molecule inhibitors could be beneficial for the treatment of malignant gliomas. METHODS We evaluated the expression of Magmas in patient-derived glioblastoma tissue samples and xenograft models. We studied the feasibility of a small molecule Magmas inhibitor (BT#9) as a therapeutic agent in stable human glioma cell lines and high-grade patient derived glioma stem-like cells. RESULTS Magmas was overexpressed in tissue sections from glioma patients and xenografts. In vivo studies revealed that BT#9 could cross the blood-brain barrier in the animal model. Magmas inhibition by BT#9 in glioma cell lines significantly decreased cell proliferation, induced apoptosis along with vacuole formation, and blocked migration and invasion. In addition, BT#9 treatment decreased the respiratory function of glioma cells, supporting the role that Magmas serves as a reactive oxygen species regulator. CONCLUSIONS This is the first study on the role of Magmas in glioma. Our findings suggest that Magmas plays a key role in glioma cell survival and targeting Magmas by small molecule inhibitors may be a therapeutic strategy in gliomas.
Collapse
Affiliation(s)
- Kaijun Di
- Department of Neurology, University of California Irvine, Irvine, CA, USA
| | - Naomi Lomeli
- Department of Pathology & Laboratory Medicine, University of California Irvine, Irvine, CA, USA
| | - Daniela A Bota
- Department of Neurology, University of California Irvine, Irvine, CA, USA. .,Department of Pathology & Laboratory Medicine, University of California Irvine, Irvine, CA, USA. .,Department of Neurological Surgery, University of California Irvine, Irvine, CA, USA. .,Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA. .,, 200 S. Manchester Ave., Suite 206, Orange, CA, 92868, USA.
| | - Bhaskar C Das
- Department of Medicine and Pharmacological Sciences, The Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
| |
Collapse
|
4
|
Lu YW, Claypool SM. Disorders of phospholipid metabolism: an emerging class of mitochondrial disease due to defects in nuclear genes. Front Genet 2015; 6:3. [PMID: 25691889 PMCID: PMC4315098 DOI: 10.3389/fgene.2015.00003] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 01/06/2015] [Indexed: 01/14/2023] Open
Abstract
The human nuclear and mitochondrial genomes co-exist within each cell. While the mitochondrial genome encodes for a limited number of proteins, transfer RNAs, and ribosomal RNAs, the vast majority of mitochondrial proteins are encoded in the nuclear genome. Of the multitude of mitochondrial disorders known to date, only a fifth are maternally inherited. The recent characterization of the mitochondrial proteome therefore serves as an important step toward delineating the nosology of a large spectrum of phenotypically heterogeneous diseases. Following the identification of the first nuclear gene defect to underlie a mitochondrial disorder, a plenitude of genetic variants that provoke mitochondrial pathophysiology have been molecularly elucidated and classified into six categories that impact: (1) oxidative phosphorylation (subunits and assembly factors); (2) mitochondrial DNA maintenance and expression; (3) mitochondrial protein import and assembly; (4) mitochondrial quality control (chaperones and proteases); (5) iron–sulfur cluster homeostasis; and (6) mitochondrial dynamics (fission and fusion). Here, we propose that an additional class of genetic variant be included in the classification schema to acknowledge the role of genetic defects in phospholipid biosynthesis, remodeling, and metabolism in mitochondrial pathophysiology. This seventh class includes a small but notable group of nuclear-encoded proteins whose dysfunction impacts normal mitochondrial phospholipid metabolism. The resulting human disorders present with a diverse array of pathologic consequences that reflect the variety of functions that phospholipids have in mitochondria and highlight the important role of proper membrane homeostasis in mitochondrial biology.
Collapse
Affiliation(s)
- Ya-Wen Lu
- Department of Physiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
| | - Steven M Claypool
- Department of Physiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
| |
Collapse
|
5
|
Srivastava S, Sinha D, Saha PP, Marthala H, D'Silva P. Magmas functions as a ROS regulator and provides cytoprotection against oxidative stress-mediated damages. Cell Death Dis 2014; 5:e1394. [PMID: 25165880 PMCID: PMC4454327 DOI: 10.1038/cddis.2014.355] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 06/25/2014] [Accepted: 07/14/2014] [Indexed: 12/14/2022]
Abstract
Redox imbalance generates multiple cellular damages leading to oxidative stress-mediated pathological conditions such as neurodegenerative diseases and cancer progression. Therefore, maintenance of reactive oxygen species (ROS) homeostasis is most important that involves well-defined antioxidant machinery. In the present study, we have identified for the first time a component of mammalian protein translocation machinery Magmas to perform a critical ROS regulatory function. Magmas overexpression has been reported in highly metabolically active tissues and cancer cells that are prone to oxidative damage. We found that Magmas regulates cellular ROS levels by controlling its production as well as scavenging. Magmas promotes cellular tolerance toward oxidative stress by enhancing antioxidant enzyme activity, thus preventing induction of apoptosis and damage to cellular components. Magmas enhances the activity of electron transport chain (ETC) complexes, causing reduced ROS production. Our results suggest that J-like domain of Magmas is essential for maintenance of redox balance. The function of Magmas as a ROS sensor was found to be independent of its role in protein import. The unique ROS modulatory role of Magmas is highlighted by its ability to increase cell tolerance to oxidative stress even in yeast model organism. The cytoprotective capability of Magmas against oxidative damage makes it an important candidate for future investigation in therapeutics of oxidative stress-related diseases.
Collapse
Affiliation(s)
- S Srivastava
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - D Sinha
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - P P Saha
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - H Marthala
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - P D'Silva
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| |
Collapse
|
6
|
Mehawej C, Delahodde A, Legeai-Mallet L, Delague V, Kaci N, Desvignes JP, Kibar Z, Capo-Chichi JM, Chouery E, Munnich A, Cormier-Daire V, Mégarbané A. The impairment of MAGMAS function in human is responsible for a severe skeletal dysplasia. PLoS Genet 2014; 10:e1004311. [PMID: 24786642 PMCID: PMC4006740 DOI: 10.1371/journal.pgen.1004311] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 03/03/2014] [Indexed: 12/17/2022] Open
Abstract
Impairment of the tightly regulated ossification process leads to a wide range of skeletal dysplasias and deciphering their molecular bases has contributed to the understanding of this complex process. Here, we report a homozygous mutation in the mitochondria-associated granulocyte macrophage colony stimulating factor-signaling gene (MAGMAS) in a novel and severe spondylodysplastic dysplasia. MAGMAS, also referred to as PAM16 (presequence translocase-associated motor 16), is a mitochondria-associated protein involved in preprotein translocation into the matrix. We show that MAGMAS is specifically expressed in trabecular bone and cartilage at early developmental stages and that the mutation leads to an instability of the protein. We further demonstrate that the mutation described here confers to yeast strains a temperature-sensitive phenotype, impairs the import of mitochondrial matrix pre-proteins and induces cell death. The finding of deleterious MAGMAS mutations in an early lethal skeletal dysplasia supports a key role for this mitochondrial protein in the ossification process. Skeletal dysplasias (SD) refer to a complex group of rare genetic disorders affecting the growth and development of the skeleton. The identification of the molecular basis of a considerable number of SD has greatly expanded our knowledge of the ossification process. Among SD, spondylodysplastic dysplasia is a generic term describing different conditions characterized by severe vertebral abnormalities and distinct by additional specific features. Several entities within this group are well defined. However, a few cases remain unclassified, of which a novel autosomal recessive spondylometaphyseal dysplasia recently reported by Mégarbané et al. in two Lebanese families. Here, we identified MAGMAS as a candidate gene responsible for this severe SD. MAGMAS, also referred to as PAM16, is a mitochondria-associated protein, involved in pre-proteins import into mitochondria and essential for cell growth and development. We demonstrated that MAGMAS is expressed in bone and cartilage in early developmental stages underlining its specific role in skeletogenesis. We also give strong evidence of the deleterious effect of the identified mutation on the in-vivo activity of Magmas and the viability of yeast strains. Reporting deleterious MAGMAS mutation in a SD supports a key and specific role for this mitochondrial protein in ossification.
Collapse
Affiliation(s)
- Cybel Mehawej
- Unité de Génétique Médicale et Laboratoire International associé INSERM à l'Unité UMR_S 910, Faculté de Médecine, Université Saint-Joseph, Beirut, Lebanon
- Département de Génétique, Unité INSERM U781, Université Paris Descartes-Sorbonne Paris Cité, Fondation Imagine, Hôpital Necker Enfants Malades, Paris, France
| | - Agnès Delahodde
- University of Paris-Sud, CNRS, UMR 8621, Institute of Genetics and Microbiology, Orsay, France
| | - Laurence Legeai-Mallet
- Département de Génétique, Unité INSERM U781, Université Paris Descartes-Sorbonne Paris Cité, Fondation Imagine, Hôpital Necker Enfants Malades, Paris, France
| | - Valérie Delague
- Inserm, UMR_S 910, Marseille, France
- Aix Marseille Université, GMGF, Marseille, France
| | - Nabil Kaci
- Département de Génétique, Unité INSERM U781, Université Paris Descartes-Sorbonne Paris Cité, Fondation Imagine, Hôpital Necker Enfants Malades, Paris, France
| | - Jean-Pierre Desvignes
- Inserm, UMR_S 910, Marseille, France
- Aix Marseille Université, GMGF, Marseille, France
| | - Zoha Kibar
- Center of Excellence in Neuroscience of Université de Montréal, Centre de Recherche du CHU Sainte-Justine, Montréal, Canada
- Department of Obstetrics and Gynecology, Université de Montréal, Montréal, Canada
| | - José-Mario Capo-Chichi
- Center of Excellence in Neuroscience of Université de Montréal, Centre de Recherche du CHU Sainte-Justine, Montréal, Canada
- Department of Obstetrics and Gynecology, Université de Montréal, Montréal, Canada
| | - Eliane Chouery
- Unité de Génétique Médicale et Laboratoire International associé INSERM à l'Unité UMR_S 910, Faculté de Médecine, Université Saint-Joseph, Beirut, Lebanon
| | - Arnold Munnich
- Département de Génétique, Unité INSERM U781, Université Paris Descartes-Sorbonne Paris Cité, Fondation Imagine, Hôpital Necker Enfants Malades, Paris, France
| | - Valérie Cormier-Daire
- Département de Génétique, Unité INSERM U781, Université Paris Descartes-Sorbonne Paris Cité, Fondation Imagine, Hôpital Necker Enfants Malades, Paris, France
| | - André Mégarbané
- Unité de Génétique Médicale et Laboratoire International associé INSERM à l'Unité UMR_S 910, Faculté de Médecine, Université Saint-Joseph, Beirut, Lebanon
- * E-mail:
| |
Collapse
|
7
|
Tagliati F, Gagliano T, Gentilin E, Minoia M, Molè D, delgi Uberti EC, Zatelli MC. Magmas overexpression inhibits staurosporine induced apoptosis in rat pituitary adenoma cell lines. PLoS One 2013; 8:e75194. [PMID: 24069394 PMCID: PMC3775776 DOI: 10.1371/journal.pone.0075194] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 08/14/2013] [Indexed: 12/22/2022] Open
Abstract
Magmas is a nuclear gene that encodes for the mitochondrial import inner membrane translocase subunit Tim16. Magmas is overexpressed in the majority of human pituitary adenomas and in a mouse ACTH-secreting pituitary adenoma cell line. Here we report that Magmas is highly expressed in two out of four rat pituitary adenoma cell lines and its expression levels inversely correlate to the extent of cellular response to staurosporine in terms of apoptosis activation and cell viability. Magmas over-expression in rat GH/PRL-secreting pituitary adenoma GH4C1 cells leads to an increase in cell viability and to a reduction in staurosporine-induced apoptosis and DNA fragmentation, in parallel with the increase in Magmas protein expression. These results indicate that Magmas plays a pivotal role in response to pro-apoptotic stimuli and confirm and extend the finding that Magmas protects pituitary cells from staurosporine-induced apoptosis, suggesting its possible involvement in pituitary adenoma development.
Collapse
Affiliation(s)
- Federico Tagliati
- Section of Endocrinology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Teresa Gagliano
- Section of Endocrinology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Erica Gentilin
- Section of Endocrinology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
- Laboratorio in rete del Tecnopolo “Tecnologie delle terapie avanzate” (LTTA) of the University of Ferrara, Ferrara, Italy
| | - Mariella Minoia
- Section of Endocrinology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Daniela Molè
- Section of Endocrinology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Ettore C. delgi Uberti
- Section of Endocrinology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
- Laboratorio in rete del Tecnopolo “Tecnologie delle terapie avanzate” (LTTA) of the University of Ferrara, Ferrara, Italy
| | - Maria Chiara Zatelli
- Section of Endocrinology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
- Laboratorio in rete del Tecnopolo “Tecnologie delle terapie avanzate” (LTTA) of the University of Ferrara, Ferrara, Italy
- * E-mail:
| |
Collapse
|
8
|
Short MK, Hallett JP, Tar K, Dange T, Schmidt M, Moir R, Willis IM, Jubinsky PT. The yeast magmas ortholog pam16 has an essential function in fermentative growth that involves sphingolipid metabolism. PLoS One 2012; 7:e39428. [PMID: 22808036 PMCID: PMC3393719 DOI: 10.1371/journal.pone.0039428] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Accepted: 05/22/2012] [Indexed: 01/06/2023] Open
Abstract
Magmas is a growth factor responsive gene encoding an essential mitochondrial protein in mammalian cells. Pam16, the Magmas ortholog in Saccharomyces cerevisiae, is a component of the presequence translocase-associated motor. A temperature-sensitive allele (pam16-I61N) was used to query an array of non-essential gene-deletion strains for synthetic genetic interactions. The pam16-I61N mutation at ambient temperature caused synthetic lethal or sick phenotypes with genes involved in lipid metabolism, perixosome synthesis, histone deacetylation and mitochondrial protein import. The gene deletion array was also screened for suppressors of the pam16-I61N growth defect to identify compensatory pathways. Five suppressor genes were identified (SUR4, ISC1, IPT1, SKN1, and FEN1) and all are involved in sphingolipid metabolism. pam16-I61N cells cultured in glucose at non-permissive temperatures resulted in rapid growth inhibition and G1 cell cycle arrest, but cell viability was maintained. Altered mitochondria morphology, reduced peroxisome induction in glycerol/ethanol and oleate, and changes in the levels of several sphingolipids including C18 alpha-hydroxy-phytoceramide, were also observed in the temperature sensitive strain. Deletion of SUR4, the strongest suppressor, reversed the temperature sensitive fermentative growth defect, the morphological changes and the elevated levels of C18 alpha-hydroxy phytoceramide in pam16-I61N. Deletion of the other four suppressor genes had similar effects on C18 alpha-hydroxy-phytoceramide levels and restored proliferation to the pam16-I61N strain. In addition, pam16-I61N inhibited respiratory growth, likely by reducing cardiolipin, which is essential for mitochondrial function. Our results suggest that the pleiotropic effects caused by impaired Pam16/Magmas function are mediated in part by changes in lipid metabolism.
Collapse
Affiliation(s)
- Mary K Short
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Jubinsky PT, Short MK, Ghanem M, Das BC. Design, synthesis, and biological activity of novel Magmas inhibitors. Bioorg Med Chem Lett 2011; 21:3479-82. [PMID: 21514823 DOI: 10.1016/j.bmcl.2011.03.050] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Revised: 03/10/2011] [Accepted: 03/14/2011] [Indexed: 11/18/2022]
Abstract
Magmas (mitochondria associated, granulocyte-macrophage colony stimulating factor signaling molecule), is a highly conserved and essential gene, expressed in all cell types. We designed and synthesized several small molecule Magmas inhibitors (SMMI) and assayed their effects on proliferation in yeast. We found that the most active compound 9 inhibited growth at the 4 μM scale. This compound was shown by fluorometric titration to bind to Magmas with a K(d)=33 μM. Target specificity of the lead compound was established by demonstrating direct binding of the compound to Magmas and by genetic studies. Molecular modeling suggested that the inhibitor bound at the predicted site in Magmas.
Collapse
Affiliation(s)
- Paul T Jubinsky
- Pediatric Hematology/Oncology, Yale University Medical School, New Haven, CT 06510, United States.
| | | | | | | |
Collapse
|
10
|
Sinha D, Joshi N, Chittoor B, Samji P, D'Silva P. Role of Magmas in protein transport and human mitochondria biogenesis. Hum Mol Genet 2010; 19:1248-62. [PMID: 20053669 PMCID: PMC2838536 DOI: 10.1093/hmg/ddq002] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Magmas, a conserved mammalian protein essential for eukaryotic development, is overexpressed in prostate carcinomas and cells exposed to granulocyte-macrophage colony-stimulating factor (GM-CSF). Reduced Magmas expression resulted in decreased proliferative rates in cultured cells. However, the cellular function of Magmas is still elusive. In this report, we have showed that human Magmas is an ortholog of Saccharomyces cerevisiae Pam16 having similar functions and is critical for protein translocation across mitochondrial inner membrane. Human Magmas shows a complete growth complementation of Δpam16 yeast cells at all temperatures. On the basis of our analysis, we report that Magmas localizes into mitochondria and is peripherally associated with inner mitochondrial membrane in yeast and humans. Magmas forms a stable subcomplex with J-protein Pam18 or DnaJC19 through its C-terminal region and is tethered to TIM23 complex of yeast and humans. Importantly, amino acid alterations in Magmas leads to reduced stability of the subcomplex with Pam18 that results in temperature sensitivity and in vivo protein translocation defects in yeast cells. These observations highlight the central role of Magmas in protein import and mitochondria biogenesis. In humans, absence of a functional DnaJC19 leads to dilated cardiac myophathic syndrome (DCM), a genetic disorder with characteristic features of cardiac myophathy and neurodegeneration. We propose that the mutations resulting in decreased stability of functional Magmas:DnaJC19 subcomplex at human TIM23 channel leads to impaired protein import and cellular respiration in DCM patients. Together, we propose a model showing how Magmas:DnaJC19 subcomplex is associated with TIM23 complex and thus regulates mitochondrial import process.
Collapse
Affiliation(s)
- Devanjan Sinha
- Department of Biochemistry, Indian Institute of Science, Bangalore, Karnataka, India
| | | | | | | | | |
Collapse
|
11
|
Elsner S, Simian D, Iosefson O, Marom M, Azem A. The mitochondrial protein translocation motor: structural conservation between the human and yeast Tim14/Pam18-Tim16/Pam16 co-chaperones. Int J Mol Sci 2009; 10:2041-2053. [PMID: 19564938 PMCID: PMC2695266 DOI: 10.3390/ijms10052041] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2009] [Revised: 04/11/2009] [Accepted: 04/14/2009] [Indexed: 01/23/2023] Open
Abstract
Most of our knowledge regarding the process of protein import into mitochondria has come from research employing Saccharomyces cerevisiae as a model system. Recently, several mammalian homologues of the mitochondrial motor proteins were identified. Of particular interest for us is the human Tim14/Pam18-Tim16/Pam16 complex. We chose a structural approach in order to examine the evolutionary conservation between yeast Tim14/Pam18-Tim16/Pam16 proteins and their human homologues. For this purpose, we examined the structural properties of the purified human proteins and their interaction with their yeast homologues, in vitro. Our results show that the soluble domains of the human Tim14/Pam18 and Tim16/Pam16 proteins interact with their yeast counterparts, forming heterodimeric complexes and that these complexes interact with yeast mtHsp70.
Collapse
Affiliation(s)
| | | | | | | | - Abdussalam Azem
- Author to whom correspondence should be addressed; E-mail:
(A.A.); Tel. + 972 3 6409007; Fax: + 972 3 6406834
| |
Collapse
|
12
|
Auth MKH, Boost KA, Leckel K, Beecken WD, Engl T, Jonas D, Oppermann E, Hilgard P, Markus BH, Bechstein WO, Blaheta RA. Controlled and reversible induction of differentiation and activation of adult human hepatocytes by a biphasic culture technique. World J Gastroenterol 2005; 11:2080-7. [PMID: 15810072 PMCID: PMC4305775 DOI: 10.3748/wjg.v11.i14.2080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: Clinical application of human hepatocytes (HC) is hampered by the progressive loss of growth and differentiation in vitro. The object of the study was to evaluate the effect of a biphasic culture technique on expression and activation of growth factor receptors and differentiation of human adult HC.
METHODS: Isolated HC were sequentially cultured in a hormone enriched differentiation medium (DM) containing nicotinamide, insulin, transferrin, selenium, and dexame-thasone or activation medium (AM) containing hepatocyte growth factor (HGF), epidermal growth factor (EGF), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Expression, distribution and activation of the HC receptors (MET and EGFR) and the pattern of characteristic cytokeratin (CK) filaments were measured by fluorometry, confocal microscopy and Western blotting.
RESULTS: In the biphasic culture system, HC underwent repeated cycles of activation (characterized by expression and activation of growth factor receptors) and re-differentiation (illustrated by distribution of typical filaments CK-18 but low or absent expression of CK-19). In AM increased expression of MET and EGFR was associated with receptor translocation into the cytoplasm and induction of atypical CK-19. In DM low expression of MET and EGFR was localized on the cell membrane and CK-19 was reduced. Receptor phosphorylation required embedding of HC in collagen type I gel.
CONCLUSION: Control and reversible modulation of growth factor receptor activation of mature human HC can be accomplished in vitro, when defined signals from the extracellular matrix and sequential growth stimuli are provided. The biphasic technique helps overcome de-differentiation, which occurs during continuous stimulation by means of growth factors.
Collapse
Affiliation(s)
- Marcus-K H Auth
- Universitäts-Kinderklinik Essen,Abteilung für Allgemeine Pädiatrie, Germany.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Jubinsky PT, Short MK, Mutema G, Morris RE, Ciraolo GM, Li M. Magmas expression in neoplastic human prostate. J Mol Histol 2005; 36:69-75. [PMID: 15704001 DOI: 10.1007/s10735-004-3840-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Revised: 09/20/2004] [Indexed: 10/25/2022]
Abstract
Magmas, is a 13-kDa mitochondrial protein which is ubiquitously expressed in eukaryotic cells. It was identified as a granulocyte-macrophage-colony stimulating factor (GM-CSF) inducible gene in hematopoietic cells and has a key role in the transport of mitochondrial proteins in yeast. Because GM-CSF receptor levels are elevated in prostate cancer, Magmas expression was examined in normal and neoplastic tissue. Magmas protein levels were barely detectable in non-neoplastic prostate glands. Increased amounts were observed in some samples of intraepithelial neoplasia. Approximately one half of the adenocarcinoma samples examined had weak Magmas expression, while the remainder had intermediate to high levels. The increased Magmas observed in malignant tissue was a result of higher protein expression and not from changes in mitochondrial content. Interestingly, in some patients, the normal prostate tissue had more Magmas message than the malignant portion. The results indicated that Magmas expression in prostate cancer is heterogeneous and independent of clinical stage and Gleason score. Further studies are needed to determine if Magmas expression has prognostic significance in prostate cancer.
Collapse
Affiliation(s)
- Paul T Jubinsky
- Division of Pediatric Hematology/Oncology, Albert Einstein College of Medicine, Bronx, NY, USA.
| | | | | | | | | | | |
Collapse
|