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Das BK, Minocha T, Kunika MD, Kannan A, Gao L, Mohan S, Xing W, Varughese KI, Zhao H. Molecular and functional mapping of Plekhm1-Rab7 interaction in osteoclasts. JBMR Plus 2024; 8:ziae034. [PMID: 38586475 PMCID: PMC10994564 DOI: 10.1093/jbmrpl/ziae034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/21/2024] [Accepted: 03/08/2024] [Indexed: 04/09/2024] Open
Abstract
Mutations in PLEKHM1 cause osteopetrosis in humans and rats. The germline and osteoclast conditional deletions of Plekhm1 gene in mice lead to defective osteoclast bone resorption and increased trabecular bone mass without overt abnormalities in other organs. As an adaptor protein, pleckstrin homology and RUN domain containing M1 (PLEKHM1) interacts with the key lysosome regulator small GTPase RAB7 via its C-terminal RUBICON homologous (RH) domain. In this study, we have conducted a structural-functional study of the PLEKHM1 RH domain and RAB7 interaction in osteoclasts in vitro. The single mutations of the key residues in the Plekhm1 RH predicted from the crystal structure of the RUBICON RH domain and RAB7 interface failed to disrupt the Plekhm1-Rab7 binding, lysosome trafficking, and bone resorption. The compound alanine mutations at Y949-R954 and L1011-I1018 regions decreased Plekhm1 protein stability and Rab7-binding, respectively, thereby attenuated lysosome trafficking and bone resorption in osteoclasts. In contrast, the compound alanine mutations at R1060-Q1068 region were dispensable for Rab7-binding and Plekhm1 function in osteoclasts. These results indicate that the regions spanning Y949-R954 and L1011-I1018 of Plekhm1 RH domain are functionally important for Plekhm1 in osteoclasts and offer the therapeutic targets for blocking bone resorption in treatment of osteoporosis and other metabolic bone diseases.
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Affiliation(s)
- Bhaba K Das
- Southern California Institute for Research and Education, VA Long Beach Healthcare System, Long Beach, CA 90822, United States
| | - Tarun Minocha
- Southern California Institute for Research and Education, VA Long Beach Healthcare System, Long Beach, CA 90822, United States
| | - Mikaela D Kunika
- Southern California Institute for Research and Education, VA Long Beach Healthcare System, Long Beach, CA 90822, United States
| | - Aarthi Kannan
- Southern California Institute for Research and Education, VA Long Beach Healthcare System, Long Beach, CA 90822, United States
- Department of Dermatology, University of California-Irvine, Irvine, CA 92697, United States
| | - Ling Gao
- Southern California Institute for Research and Education, VA Long Beach Healthcare System, Long Beach, CA 90822, United States
- Department of Dermatology, University of California-Irvine, Irvine, CA 92697, United States
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, United States
| | - Weirong Xing
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, United States
| | - Kottayil I Varughese
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock 72205, AR, United States
| | - Haibo Zhao
- Southern California Institute for Research and Education, VA Long Beach Healthcare System, Long Beach, CA 90822, United States
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Huybrechts Y, Van Hul W. Osteopetrosis associated with PLEKHM1 and SNX10 genes, both involved in osteoclast vesicular trafficking. Bone 2022; 164:116520. [PMID: 35981699 DOI: 10.1016/j.bone.2022.116520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 08/09/2022] [Accepted: 08/11/2022] [Indexed: 11/24/2022]
Abstract
The clinical and radiological variability seen in different forms of osteopetrosis, all due to impaired osteoclastic bone resorption, reflect many causal genes. Both defective differentiation of osteoclasts from hematopoietic stem cells as well as disturbed functioning of osteoclasts can be the underlying pathogenic mechanism. Pathogenic variants in PLEKHM1 and SNX10 can be classified among the latter as they impair vesicular transport within the osteoclast and therefore result in the absence of a ruffled border. Some of the typical radiological hallmarks of osteopetrosis can be seen, and most cases present as a relatively mild form segregating in an autosomal recessive mode of inheritance.
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Affiliation(s)
- Yentl Huybrechts
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
| | - Wim Van Hul
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium.
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Roy M, Roux S. Rab GTPases in Osteoclastic Bone Resorption and Autophagy. Int J Mol Sci 2020; 21:ijms21207655. [PMID: 33081155 PMCID: PMC7589333 DOI: 10.3390/ijms21207655] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/11/2020] [Accepted: 10/13/2020] [Indexed: 12/17/2022] Open
Abstract
Small guanosine triphosphate hydrolases (GTPases) of the Rab family are involved in plasma membrane delivery, fusion events, and lysosomal and autophagic degradation pathways, thereby regulating signaling pathways and cell differentiation and function. Osteoclasts are bone-resorbing cells that maintain bone homeostasis. Polarized vesicular trafficking pathways result in the formation of the ruffled border, the osteoclast’s resorptive organelle, which also assists in transcytosis. Here, we reviewed the different roles of Rab GTPases in the endomembrane machinery of osteoclasts and in bone diseases caused by the dysfunction of these proteins, with a particular focus on autophagy and bone resorption. Understanding the molecular mechanisms underlying osteoclast-related bone disease development is critical for developing and improving therapies.
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Rab GTPases in Osteoclastic Endomembrane Systems. BIOMED RESEARCH INTERNATIONAL 2018; 2018:4541538. [PMID: 30186859 PMCID: PMC6114073 DOI: 10.1155/2018/4541538] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 07/18/2018] [Indexed: 12/13/2022]
Abstract
Osteoclasts (OCs) are bone-resorbing cells that maintain bone homeostasis. OC differentiation, survival, and activity are regulated by numerous small GTPases, including those of the Rab family, which are involved in plasma membrane delivery and lysosomal and autophagic degradation pathways. In resorbing OCs, polarized vesicular trafficking pathways also result in formation of the ruffled membrane, the resorbing organelle, and in transcytosis.
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Just F, Reyer H, Muráni E, Ponsuksili S, Oster M, Wimmers K. Genetic variants of major genes contributing to phosphate and calcium homeostasis and their association with serum parameters in pigs. J Appl Genet 2018; 59:325-333. [PMID: 29931419 PMCID: PMC6061000 DOI: 10.1007/s13353-018-0449-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 04/12/2018] [Accepted: 06/08/2018] [Indexed: 12/29/2022]
Abstract
Calcium and phosphorus are irreplaceable components of life. Tracking the fate of calcium and phosphorus in organisms deserves high attention due to their relevance in bone metabolism and subsequently animal health. Indeed, bone serves as reservoir for calcium and phosphorus, whose formation and resorption follow specific molecular routes including hormones, receptors, and transcription factors. The objective of the study was to analyze the genetic variation of major components driving mineral utilization such as calcitonin receptor, calcium sensing receptor, fibroblast growth factor 23 (FGF23), parathyroid hormone receptor, osteopontin, stanniocalcin 1, RAF-type zinc finger domain containing 1 (TRAFD1), and vitamin D receptor. A German Landrace pig population (n = 360) was used to perform an association analysis between selected single nucleotide polymorphisms (SNP) and relevant serum parameters (calcium, phosphorus, calcium/phosphorus ratio, alkaline phosphatase). Analyzed SNPs in FGF23 (rs710498025) and TRAFD1 (rs345195312) were significantly (p ≤ 0.05) associated with the serum calcium/phosphorus ratio and serum phosphorus levels, respectively. This might represent a modulation of the homeostatic balance between calcium and phosphorus. Furthermore, TRAFD1 is known to be involved in skeletal disorders which emphasize its link to phosphorus utilization and immune system. However, none of the analyzed genetic variants of these major regulators of phosphate and calcium homeostasis showed significant associations after correction for multiple testing (q value > 0.05). Thus, minor contributors as well as unknown and yet to be elucidated regulators of mineral homeostasis need to be characterized towards the implementation of improved phosphorus efficiency in pig breeding programs.
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Affiliation(s)
- Franziska Just
- Institute of Genome Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany
| | - Henry Reyer
- Institute of Genome Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany
| | - Eduard Muráni
- Institute of Genome Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany
| | - Siriluck Ponsuksili
- Institute of Genome Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany
| | - Michael Oster
- Institute of Genome Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany
| | - Klaus Wimmers
- Institute of Genome Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany. .,Faculty of Agricultural and Environmental Sciences, University Rostock, 18059, Rostock, Germany.
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Abstract
PURPOSE OF REVIEW The term osteopetrosis refers to a group of rare skeletal diseases sharing the hallmark of a generalized increase in bone density owing to a defect in bone resorption. Osteopetrosis is clinically and genetically heterogeneous, and a precise molecular classification is relevant for prognosis and treatment. Here, we review recent data on the pathogenesis of this disorder. RECENT FINDINGS Novel mutations in known genes as well as defects in new genes have been recently reported, further expanding the spectrum of molecular defects leading to osteopetrosis. Exploitation of next-generation sequencing tools is ever spreading, facilitating differential diagnosis. Some complex phenotypes in which osteopetrosis is accompanied by additional clinical features have received a molecular classification, also involving new genes. Moreover, novel types of mutations have been recognized, which for their nature or genomic location are at high risk being neglected. Yet, the causative mutation is unknown in some patients, indicating that the genetics of osteopetrosis still deserves intense research efforts.
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Affiliation(s)
- Eleonora Palagano
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy
- Department of Medical Biotechnologies and Translational Medicine, University of Milan, Milan, Italy
| | - Ciro Menale
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy
- Milan Unit, CNR-IRGB, Milan, Italy
| | - Cristina Sobacchi
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy.
- Milan Unit, CNR-IRGB, Milan, Italy.
| | - Anna Villa
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy
- Milan Unit, CNR-IRGB, Milan, Italy
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Salmonella exploits the host endolysosomal tethering factor HOPS complex to promote its intravacuolar replication. PLoS Pathog 2017; 13:e1006700. [PMID: 29084291 PMCID: PMC5679646 DOI: 10.1371/journal.ppat.1006700] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 11/09/2017] [Accepted: 10/18/2017] [Indexed: 12/22/2022] Open
Abstract
Salmonella enterica serovar typhimurium extensively remodels the host late endocytic compartments to establish its vacuolar niche within the host cells conducive for its replication, also known as the Salmonella-containing vacuole (SCV). By maintaining a prolonged interaction with late endosomes and lysosomes of the host cells in the form of interconnected network of tubules (Salmonella-induced filaments or SIFs), Salmonella gains access to both membrane and fluid-phase cargo from these compartments. This is essential for maintaining SCV membrane integrity and for bacterial intravacuolar nutrition. Here, we have identified the multisubunit lysosomal tethering factor—HOPS (HOmotypic fusion and Protein Sorting) complex as a crucial host factor facilitating delivery of late endosomal and lysosomal content to SCVs, providing membrane for SIF formation, and nutrients for intravacuolar bacterial replication. Accordingly, depletion of HOPS subunits significantly reduced the bacterial load in non-phagocytic and phagocytic cells as well as in a mouse model of Salmonella infection. We found that Salmonella effector SifA in complex with its binding partner; SKIP, interacts with HOPS subunit Vps39 and mediates recruitment of this tethering factor to SCV compartments. The lysosomal small GTPase Arl8b that binds to, and promotes membrane localization of Vps41 (and other HOPS subunits) was also required for HOPS recruitment to SCVs and SIFs. Our findings suggest that Salmonella recruits the host late endosomal and lysosomal membrane fusion machinery to its vacuolar niche for access to host membrane and nutrients, ensuring its intracellular survival and replication. Intracellular pathogens have devised various strategies to subvert the host membrane trafficking pathways for their growth and survival inside the host cells. Salmonella is one such successful intracellular pathogen that redirects membrane and nutrients from the host endocytic compartments to its replicative niche known as the Salmonella-containing vacuole (SCV) via establishing an interconnected network of tubules (Salmonella-induced filaments or SIFs) that form a continuum with the SCVs. How Salmonella ensures a constant supply of endocytic cargo required for its survival and growth remained unexplored. Our work uncovers a strategy evolved by Salmonella wherein it secretes a bacterial effector into the host cytosol that recruits component of host vesicle fusion machinery-HOPS complex to SCVs and SIFs. HOPS complex promotes docking of the late endocytic compartments at the SCV membrane, prior to their fusion. Thus, depletion of HOPS subunits both in cultured cell lines as well as a mouse model inhibits Salmonella replication, likely due to reduced access to host membranes and nutrients by the vacuolar bacteria. These findings provide mechanistic insights into how this pathogen reroutes the host’s endocytic transport towards its vacuole, ensuring its own intracellular survival and replication.
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Marwaha R, Arya SB, Jagga D, Kaur H, Tuli A, Sharma M. The Rab7 effector PLEKHM1 binds Arl8b to promote cargo traffic to lysosomes. J Cell Biol 2017; 216:1051-1070. [PMID: 28325809 PMCID: PMC5379943 DOI: 10.1083/jcb.201607085] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 12/30/2016] [Accepted: 02/06/2017] [Indexed: 01/03/2023] Open
Abstract
Endocytic, autophagic, and phagocytic vesicles move on microtubule tracks to fuse with lysosomes. Small GTPases, such as Rab7 and Arl8b, recruit their downstream effectors to mediate this transport and fusion. However, the potential cross talk between these two GTPases is unclear. Here, we show that the Rab7 effector PLEKHM1 simultaneously binds Rab7 and Arl8b, bringing about clustering and fusion of late endosomes and lysosomes. We show that the N-terminal RUN domain of PLEKHM1 is necessary and sufficient for interaction with Arl8b and its subsequent localization to lysosomes. Notably, we also demonstrate that Arl8b mediates recruitment of HOPS complex to PLEKHM1-positive vesicle contact sites. Consequently, Arl8b binding to PLEKHM1 is required for its function in delivery and, therefore, degradation of endocytic and autophagic cargo in lysosomes. Finally, we also show that PLEKHM1 competes with SKIP for Arl8b binding, which dictates lysosome positioning. These findings suggest that Arl8b, along with its effectors, orchestrates lysosomal transport and fusion.
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Affiliation(s)
- Rituraj Marwaha
- Department of Biological Sciences, Indian Institute of Science Education and Research, Mohali, Punjab 140306, India
| | - Subhash B Arya
- Division of Cell Biology and Immunology, Council of Scientific and Industrial Research, Institute of Microbial Technology, Chandigarh 160036, India
| | - Divya Jagga
- Division of Cell Biology and Immunology, Council of Scientific and Industrial Research, Institute of Microbial Technology, Chandigarh 160036, India
| | - Harmeet Kaur
- Division of Cell Biology and Immunology, Council of Scientific and Industrial Research, Institute of Microbial Technology, Chandigarh 160036, India
| | - Amit Tuli
- Division of Cell Biology and Immunology, Council of Scientific and Industrial Research, Institute of Microbial Technology, Chandigarh 160036, India
| | - Mahak Sharma
- Department of Biological Sciences, Indian Institute of Science Education and Research, Mohali, Punjab 140306, India
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