Segeletz S, Danglot L, Galli T, Hoflack B. ARAP1 Bridges Actin Dynamics and AP-3-Dependent Membrane Traffic in Bone-Digesting Osteoclasts.
iScience 2018;
6:199-211. [PMID:
30240610 PMCID:
PMC6137390 DOI:
10.1016/j.isci.2018.07.019]
[Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/06/2018] [Accepted: 07/20/2018] [Indexed: 12/23/2022] Open
Abstract
Bone-resorbing osteoclasts play a central role in bone remodeling and its pathology. To digest bone, osteoclasts re-organize both F-actin, to assemble podosomes/sealing zones, and membrane traffic, to form bone-facing ruffled borders enriched in lysosomal membrane proteins. It remains elusive how these processes are coordinated. Here, we show that ARAP1 (ArfGAP with RhoGAP domain, ankyrin repeat and PH domain-containing protein 1) fulfills this function. At podosomes/sealing zones, ARAP1 is part of a protein complex where its RhoGAP domain regulates actin dynamics. At endosomes, ARAP1 interacts with AP-3 adaptor complexes where its Arf-GAP domain regulates the Arf1-dependent AP-3 binding to membranes and, consequently lysosomal membrane protein transport to ruffled borders. Accordingly, ARAP1 or AP-3 depletion in osteoclasts alters their capacity to digest bone in vitro. and AP-3δ-deficient mocha mice, a model of the Hermansky-Pudlak storage pool syndrome, develop osteoporosis. Thus, ARAP1 bridges F-actin and membrane dynamics in osteoclasts for proper bone homeostasis.
ARAP1 is a bridging factor controlling actin and membrane dynamics in osteoclasts
ARAP1 controls podosome dynamics and AP-3 coat recruitment to membranes
AP-3 controls targeting of lysosomal membrane proteins to the ruffled border
AP-3-deficient mocha mice develop osteoporosis
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