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Pulli K, Saarimäki-Vire J, Ahonen P, Liu X, Ibrahim H, Chandra V, Santambrogio A, Wang Y, Vaaralahti K, Iivonen AP, Känsäkoski J, Tommiska J, Kemkem Y, Varjosalo M, Vuoristo S, Andoniadou CL, Otonkoski T, Raivio T. A splice site variant in MADD affects hormone expression in pancreatic β cells and pituitary gonadotropes. JCI Insight 2024; 9:e167598. [PMID: 38775154 PMCID: PMC11141940 DOI: 10.1172/jci.insight.167598] [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: 06/27/2023] [Accepted: 04/12/2024] [Indexed: 06/02/2024] Open
Abstract
MAPK activating death domain (MADD) is a multifunctional protein regulating small GTPases RAB3 and RAB27, MAPK signaling, and cell survival. Polymorphisms in the MADD locus are associated with glycemic traits, but patients with biallelic variants in MADD manifest a complex syndrome affecting nervous, endocrine, exocrine, and hematological systems. We identified a homozygous splice site variant in MADD in 2 siblings with developmental delay, diabetes, congenital hypogonadotropic hypogonadism, and growth hormone deficiency. This variant led to skipping of exon 30 and in-frame deletion of 36 amino acids. To elucidate how this mutation causes pleiotropic endocrine phenotypes, we generated relevant cellular models with deletion of MADD exon 30 (dex30). We observed reduced numbers of β cells, decreased insulin content, and increased proinsulin-to-insulin ratio in dex30 human embryonic stem cell-derived pancreatic islets. Concordantly, dex30 led to decreased insulin expression in human β cell line EndoC-βH1. Furthermore, dex30 resulted in decreased luteinizing hormone expression in mouse pituitary gonadotrope cell line LβT2 but did not affect ontogeny of stem cell-derived GnRH neurons. Protein-protein interactions of wild-type and dex30 MADD revealed changes affecting multiple signaling pathways, while the GDP/GTP exchange activity of dex30 MADD remained intact. Our results suggest MADD-specific processes regulate hormone expression in pancreatic β cells and pituitary gonadotropes.
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Affiliation(s)
- Kristiina Pulli
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Jonna Saarimäki-Vire
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Pekka Ahonen
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Xiaonan Liu
- Institute of Biotechnology, Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Hazem Ibrahim
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Vikash Chandra
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Alice Santambrogio
- Centre for Craniofacial and Regenerative Biology, King’s College London, London, United Kingdom
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Yafei Wang
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Kirsi Vaaralahti
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Anna-Pauliina Iivonen
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Johanna Känsäkoski
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Physiology, Faculty of Medicine
| | - Johanna Tommiska
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Physiology, Faculty of Medicine
| | - Yasmine Kemkem
- Centre for Craniofacial and Regenerative Biology, King’s College London, London, United Kingdom
| | - Markku Varjosalo
- Institute of Biotechnology, Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Sanna Vuoristo
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Obstetrics and Gynecology; and
- HiLIFE, University of Helsinki, Helsinki, Finland
| | - Cynthia L. Andoniadou
- Centre for Craniofacial and Regenerative Biology, King’s College London, London, United Kingdom
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- New Children’s Hospital, Helsinki University Hospital, Pediatric Research Center, Helsinki, Finland
| | - Taneli Raivio
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Physiology, Faculty of Medicine
- New Children’s Hospital, Helsinki University Hospital, Pediatric Research Center, Helsinki, Finland
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Medlyn MJ, Maeder E, Bradley C, Phatarpekar P, Ham H, Billadeau DD. MADD regulates natural killer cell degranulation through Rab27a activation. J Cell Sci 2024; 137:jcs261582. [PMID: 38506245 PMCID: PMC11058345 DOI: 10.1242/jcs.261582] [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: 09/05/2023] [Accepted: 03/07/2024] [Indexed: 03/21/2024] Open
Abstract
Natural killer (NK) cells have the ability to lyse other cells through the release of lytic granules (LGs). This is in part mediated by the small GTPase Rab27a, which was first identified to play a crucial role in degranulation through the study of individuals harboring mutations in the gene encoding Rab27a. However, the guanine nucleotide exchange factor (GEF) regulating the activation of Rab27a in cytotoxic lymphocytes was unknown. Here, we show that knockout of MADD significantly decreased the levels of GTP-bound Rab27a in both resting and stimulated NK cells, and MADD-deficient NK cells and CD8+ T cells displayed severely reduced degranulation and cytolytic ability, similar to that seen with Rab27a deficiency. Although MADD colocalized with Rab27a on LGs and was enriched at the cytolytic synapse, the loss of MADD did not impact Rab27a association with LGs nor their recruitment to the cytolytic synapse. Together, our results demonstrate an important role for MADD in cytotoxic lymphocyte killing.
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Affiliation(s)
- Michael J. Medlyn
- Department of Immunology College of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Easton Maeder
- Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
| | - Claire Bradley
- Department of Immunology College of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Hyoungjun Ham
- Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
| | - Daniel D. Billadeau
- Department of Immunology College of Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
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Darouich S, Darouich S. Calloso-adreno-scrotal agenesis associated with biallelic MAPK-activating death domain protein (MADD) variant: Further phenotypic delineation of MADD deficiency. Am J Med Genet A 2024; 194:e63463. [PMID: 37932938 DOI: 10.1002/ajmg.a.63463] [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: 07/06/2023] [Revised: 09/22/2023] [Accepted: 10/20/2023] [Indexed: 11/08/2023]
Abstract
MAPK-activating death domain protein (MADD) deficiency is associated with a broad clinical spectrum ranging from mild developmental impairment to fatal multisystem disorder. We report an additional case of severe form with some overlapping and unreported systemic features in a growth-restricted full-term male newborn. The novel findings include corpus callosum agenesis, bilateral adrenal agenesis, scrotal aplasia, and abnormal skin pigmentation. Microscopic changes are only remarkable in thyroid gland that shows decreased, variously sized follicles with absent or non-vacuolated pale colloid. This unique constellation of birth defects is associated with a novel homozygous in-frame MADD gene deletion (NM_003682.4: c.4853_4855delGCT:p.Cys1618del). This case report expands the phenotypic and genetic spectrum of MADD deficiency.
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Affiliation(s)
- Sihem Darouich
- Faculté de Médecine de Tunis, Université de Tunis El Manar, Tunis, Tunisia
- Unité de Pathologie Fœtale et Placentaire, CHU Habib Bougatfa, Bizerte, Tunisia
| | - Samia Darouich
- Institut supérieur des Sciences Humaines de Tunis, Université de Tunis El Manar, Tunis, Tunisia
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GDP/GTP exchange factor MADD drives activation and recruitment of secretory Rab GTPases to Weibel-Palade bodies. Blood Adv 2021; 5:5116-5127. [PMID: 34551092 PMCID: PMC9153003 DOI: 10.1182/bloodadvances.2021004827] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 07/19/2021] [Indexed: 02/02/2023] Open
Abstract
von Willebrand factor (VWF) is an essential hemostatic protein that is synthesized and secreted by endothelial cells and stored in Weibel-Palade bodies (WPBs). The secretory Rab GTPases Rab27A, Rab3B, and Rab3D have been linked with WPB trafficking and secretion. How these Rabs are activated and recruited to WPBs remains elusive. In this study, we identified MAP kinase-activating death domain (MADD) as the guanine nucleotide exchange factor for Rab27A and both Rab3 isoforms in primary human endothelial cells. Rab activity assays revealed a reduction in Rab27A, Rab3B, and Rab3D activation upon MADD silencing. Rab activation, but not binding, was dependent on the differentially expressed in normal and neoplastic cells (DENN) domain of MADD, indicating the potential existence of 2 Rab interaction modules. Furthermore, immunofluorescent analysis showed that Rab27A, Rab3B, and Rab3D recruitment to WPBs was dramatically decreased upon MADD knockdown, revealing that MADD drives Rab membrane targeting. Artificial mistargeting of MADD using a TOMM70 tag abolished Rab27A localization to WPB membranes in a DENN domain-dependent manner, indicating that normal MADD localization in the cytosol is crucial. Activation of Rab3B and Rab3D was reduced upon Rab27A silencing, suggesting that activation of these Rabs is enhanced through previous activation of Rab27A by MADD. MADD silencing did not affect WPB morphology, but it did reduce VWF intracellular content. Furthermore, MADD-depleted cells exhibited decreased histamine-evoked VWF release, similar to Rab27A-depleted cells. In conclusion, MADD acts as a master regulator of VWF secretion by coordinating the activation and membrane targeting of secretory Rabs to WPBs.
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Izumi T. In vivo Roles of Rab27 and Its Effectors in Exocytosis. Cell Struct Funct 2021; 46:79-94. [PMID: 34483204 PMCID: PMC10511049 DOI: 10.1247/csf.21043] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
The monomeric GTPase Rab27 regulates exocytosis of a broad range of vesicles in multicellular organisms. Several effectors bind GTP-bound Rab27a and/or Rab27b on secretory vesicles to execute a series of exocytic steps, such as vesicle maturation, movement along microtubules, anchoring within the peripheral F-actin network, and tethering to the plasma membrane, via interactions with specific proteins and membrane lipids in a local milieu. Although Rab27 effectors generally promote exocytosis, they can also temporarily restrict it when they are involved in the rate-limiting step. Genetic alterations in Rab27-related molecules cause discrete diseases manifesting pigment dilution and immunodeficiency, and can also affect common diseases such as diabetes and cancer in complex ways. Although the function and mechanism of action of these effectors have been explored, it is unclear how multiple effectors act in coordination within a cell to regulate the secretory process as a whole. It seems that Rab27 and various effectors constitutively reside on individual vesicles to perform consecutive exocytic steps. The present review describes the unique properties and in vivo roles of the Rab27 system, and the functional relationship among different effectors coexpressed in single cells, with pancreatic beta cells used as an example.Key words: membrane trafficking, regulated exocytosis, insulin granules, pancreatic beta cells.
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Affiliation(s)
- Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
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Fukuda M. Rab GTPases: Key players in melanosome biogenesis, transport, and transfer. Pigment Cell Melanoma Res 2020; 34:222-235. [PMID: 32997883 DOI: 10.1111/pcmr.12931] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 09/23/2020] [Indexed: 12/12/2022]
Abstract
Melanosomes are specialized intracellular organelles that produce and store melanin pigments in melanocytes, which are present in several mammalian tissues and organs, including the skin, hair, and eyes. Melanosomes form and mature stepwise (stages I-IV) in melanocytes and then are transported toward the plasma membrane along the cytoskeleton. They are subsequently transferred to neighboring keratinocytes by a largely unknown mechanism, and incorporated melanosomes are transported to the perinuclear region of the keratinocytes where they form melanin caps. Melanocytes also extend several dendrites that facilitate the efficient transfer of the melanosomes to the keratinocytes. Since the melanosome biogenesis, transport, and transfer steps require multiple membrane trafficking processes, Rab GTPases that are conserved key regulators of membrane traffic in all eukaryotes are crucial for skin and hair pigmentation. Dysfunctions of two Rab isoforms, Rab27A and Rab38, are known to cause a hypopigmentation phenotype in human type 2 Griscelli syndrome patients and in chocolate mice (related to Hermansky-Pudlak syndrome), respectively. In this review article, I review the literature on the functions of each Rab isoform and its upstream and downstream regulators in mammalian melanocytes and keratinocytes.
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Affiliation(s)
- Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, Japan
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Homma Y, Hiragi S, Fukuda M. Rab family of small GTPases: an updated view on their regulation and functions. FEBS J 2020; 288:36-55. [PMID: 32542850 PMCID: PMC7818423 DOI: 10.1111/febs.15453] [Citation(s) in RCA: 206] [Impact Index Per Article: 51.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 05/27/2020] [Accepted: 06/11/2020] [Indexed: 12/13/2022]
Abstract
The Rab family of small GTPases regulates intracellular membrane trafficking by orchestrating the biogenesis, transport, tethering, and fusion of membrane‐bound organelles and vesicles. Like other small GTPases, Rabs cycle between two states, an active (GTP‐loaded) state and an inactive (GDP‐loaded) state, and their cycling is catalyzed by guanine nucleotide exchange factors (GEFs) and GTPase‐activating proteins (GAPs). Because an active form of each Rab localizes on a specific organelle (or vesicle) and recruits various effector proteins to facilitate each step of membrane trafficking, knowing when and where Rabs are activated and what effectors Rabs recruit is crucial to understand their functions. Since the discovery of Rabs, they have been regarded as one of the central hubs for membrane trafficking, and numerous biochemical and genetic studies have revealed the mechanisms of Rab functions in recent years. The results of these studies have included the identification and characterization of novel GEFs, GAPs, and effectors, as well as post‐translational modifications, for example, phosphorylation, of Rabs. Rab functions beyond the simple effector‐recruiting model are also emerging. Furthermore, the recently developed CRISPR/Cas technology has enabled acceleration of knockout analyses in both animals and cultured cells and revealed previously unknown physiological roles of many Rabs. In this review article, we provide the most up‐to‐date and comprehensive lists of GEFs, GAPs, effectors, and knockout phenotypes of mammalian Rabs and discuss recent findings in regard to their regulation and functions.
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Affiliation(s)
- Yuta Homma
- Laboratory of Membrane Trafficking Mechanisms, Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Shu Hiragi
- Laboratory of Membrane Trafficking Mechanisms, Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
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Abstract
Melanin pigments are responsible for human skin and hair color, and they protect the body from harmful ultraviolet light. The black and brown melanin pigments are synthesized in specialized lysosome-related organelles called melanosomes in melanocytes. Mature melanosomes are transported within melanocytes and transferred to adjacent keratinocytes, which constitute the principal part of human skin. The melanosomes are then deposited inside the keratinocytes and darken the skin (a process called tanning). Owing to their dark color, melanosomes can be seen easily with an ordinary light microscope, and melanosome research dates back approximately 150 years; since then, biochemical studies aimed at isolating and purifying melanosomes have been conducted. Moreover, in the last two decades, hundreds of molecules involved in regulating melanosomal functions have been identified by analyses of the genes of coat-color mutant animals and patients with genetic diseases characterized by pigment abnormalities, such as hypopigmentation. In recent years, dynamic analyses by more precise microscopic observations have revealed specific functions of a variety of molecules involved in melanogenesis. This review article focuses on the latest findings with regard to the steps (or mechanisms) involved in melanosome formation and transport of mature melanosomes within epidermal melanocytes. Finally, we will touch on current topics in melanosome research, particularly on the "melanosome transfer" and "post-transfer" steps, and discuss future directions in pigment research.
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Affiliation(s)
- Norihiko Ohbayashi
- Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba 305-8575, Japan
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Miyagi 980-8578, Japan
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