Caveolin-associated filamentous actin (Cav-actin) defines a novel F-actin structure in adipocytes.
Dynamic actin remodeling has been implicated in the translocation of the insulin-responsive glucose transporter 4 (GLUT4) to the plasma membrane in adipocytes. Here we show that fully differentiated 3T3L1 adipocytes have unique cortical filamentous actin structure, designated Cav-actin (caveolae-associated F-actin). During 3T3L1 adipocyte differentiation, rhodamine-phalloidin staining demonstrated the formation of a cortical actin cytoskeleton that is composed of small dot-like F-actin spikes lining the inside of the plasma membrane. Double labeling with a caveolin antibody indicated that these F-actin spikes emanate from organized rosette-like clusters of caveolae/lipid raft microdomains. In contrast, there was no obvious relationship between F-actin and caveolin localization and/or organization in 3T3L1 preadipocytes (fibroblasts). Treatments of differentiated adipocytes with latrunculin B, Clostridium difficile toxin B or a dominant-interfering TC10 mutant (TC10/T31N) disrupted the Cav-actin structure without significantly affecting the organization of clustered caveolae. Similarly, disruption of the clustered caveolae with methyl-beta-cyclodextrin also dispersed the Cav-actin structure. These data demonstrate that this novel Cav-actin structure is organized through clustered caveolae but that the formation of caveolae-rosettes are not dependent upon F-actin.
Kanzaki
Makoto
M
Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242-1109, USA.
Pessin
Jeffrey E
JE
D016475:3T3 Cells; D000199:Actins / Q000737:chemistry*; D017667:Adipocytes / Q000737:chemistry* / Q000187:drug effects; D000818:Animals; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D022461:Caveolins / Q000737:chemistry*; D002454:Cell Differentiation / Q000187:drug effects; D003599:Cytoskeleton / Q000648:ultrastructure; D005347:Fibroblasts / Q000187:drug effects / Q000648:ultrastructure; D007202:Indicators and Reagents; D051379:Mice; D010590:Phalloidine; D012235:Rhodamines; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
D000199:Actins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D022461:Caveolins; D007202:Indicators and Reagents; D012235:Rhodamines; D013844:Thiazoles; D053778:Thiazolidines; C031815:toxB protein, Clostridium difficile; D010590:Phalloidine; C037068:latrunculin B