Genetic and pharmacological inhibition of Rho-associated kinase II enhances adipogenesis.
Rho-associated kinase (ROCK) regulates reorganization of actin cytoskeleton. During adipogenesis, the structure of filamentous actin is converted from long stress fibers to cortical actin, suggesting that the ROCK is involved in adipogenesis. Two ROCK isoforms have been identified: ROCK-I and ROCK-II. However, pharmacological inhibitors of ROCK cannot distinguish two ROCK isoforms. In the present study, we examined the role of ROCK in adipogenesis and actin cytoskeleton using genetic and pharmacological approaches. Y-27632, which inhibits the activity of both ROCK isoforms, enhanced adipogenesis through the up-regulation of adipogenic transcription factors in 3T3-L1 cells. Furthermore, Y-27632 restored inhibition of adipogenesis by lysophosphatidic acid, which activates Rho. Regarding actin cytoskeleton, Y-27632 disrupted stress fibers in 3T3-L1 preadipocytes. Next, we analyzed adipogenesis of mouse embryonic fibroblasts (MEFs) derived from ROCK-I and ROCK-II knock-out mice, respectively. Adipogenesis of ROCK-II (-/-) MEFs was markedly enhanced compared with wild-type MEFs while that of ROCK-I (-/-) MEFs was not. In contrast to pharmacological approaches, no obvious alteration was found in actin cytoskeleton of ROCK-II (-/-) MEFs compared with wild-type MEFs. In 3T3-L1 cells, knockdown of ROCK-II by RNA interference enhanced the expression of adipogenic transcription factors while that of ROCK-I did not. Moreover, Y-27632 inhibited IRS-1 serine phosphorylation and enhanced Akt phosphorylation in 3T3-L1 preadipocytes. Similarly, Akt phosphorylation in ROCK-II (-/-) MEFs was augmented compared with wild-type MEFs. In conclusion, inhibition of ROCK-II, not ROCK-I, enhances adipogenesis accompanied by the up-regulation of adipogenic transcription factors. Augmentation of insulin signaling may contribute to the enhancement of adipogenesis.
Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto 606-8507, Japan.
Michio
M
Noguchi
Kiminori
K
Hosoda
Junji
J
Fujikura
Muneya
M
Fujimoto
Hiroshi
H
Iwakura
Tsutomu
T
Tomita
Takako
T
Ishii
Naoki
N
Arai
Masakazu
M
Hirata
Ken
K
Ebihara
Hiroaki
H
Masuzaki
Hiroshi
H
Itoh
Shuh
S
Narumiya
Kazuwa
K
Nakao
D041721:3T3-L1 Cells; D000199:Actins / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D050156:Adipogenesis / Q000187:drug effects; D000818:Animals; D003599:Cytoskeleton / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D008957:Models, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D054460:rho-Associated Kinases
D000199:Actins; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases