Identification of CAP as a costameric protein that interacts with filamin C.
Cbl-associated protein (CAP) is an adaptor protein that interacts with both signaling and cytoskeletal proteins. Here, we characterize the expression, localization and potential function of CAP in striated muscle. CAP is markedly induced during myoblast differentiation, and colocalizes with vinculin during costamerogenesis. In adult mice, CAP is enriched in oxidative muscle fibers, and it is found in membrane anchorage complexes, including intercalated discs, costameres, and myotendinous junctions. Using both yeast two-hybrid and proteomic approaches, we identified the sarcomeric protein filamin C (FLNc) as a binding partner for CAP. When overexpressed, CAP recruits FLNc to cell-extracellular matrix adhesions, where the two proteins cooperatively regulate actin reorganization. Moreover, overexpression of CAP inhibits FLNc-induced cell spreading on fibronectin. In dystrophin-deficient mdx mice, the expression and membrane localization of CAP is increased, concomitant with the elevated plasma membrane content of FLNc, suggesting that CAP may compensate for the reduced membrane linkage of the myofibrils due to the loss of the dystroglycan-sarcoglycan complex in these mice. Thus, through its interaction with FLNc, CAP provides another link between the myofibril cytoskeleton and the plasma membrane of muscle cells, and it may play a dynamic role in the regulation and maintenance of muscle structural integrity.
Zhang
Mei
M
Departments of Internal Medicine and Physiology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.
Liu
Jun
J
Cheng
Alan
A
Deyoung
Stephanie M
SM
Saltiel
Alan R
AR
D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion; D002454:Cell Differentiation; D002460:Cell Line; D002522:Chlorocebus aethiops; D003285:Contractile Proteins / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D064448:Filamins; D005786:Gene Expression Regulation; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D024510:Muscle Development; D009132:Muscles / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding
D000199:Actins; D003285:Contractile Proteins; D005353:Fibronectins; D064448:Filamins; D008840:Microfilament Proteins; C119201:ponsin