The rho-guanine nucleotide exchange factor domain of obscurin activates rhoA signaling in skeletal muscle.

Journal Article (Journal Article)

Obscurin is a large ( approximately 800-kDa), modular protein of striated muscle that concentrates around the M-bands and Z-disks of each sarcomere, where it is well positioned to sense contractile activity. Obscurin contains several signaling domains, including a rho-guanine nucleotide exchange factor (rhoGEF) domain and tandem pleckstrin homology domain, consistent with a role in rho signaling in muscle. We investigated the ability of obscurin's rhoGEF domain to interact with and activate small GTPases. Using a combination of in vitro and in vivo approaches, we found that the rhoGEF domain of obscurin binds selectively to rhoA, and that rhoA colocalizes with obscurin at the M-band in skeletal muscle. Other small GTPases, including rac1 and cdc42, neither associate with the rhoGEF domain of obscurin nor concentrate at the level of the M-bands. Furthermore, overexpression of the rhoGEF domain of obscurin in adult skeletal muscle selectively increases rhoA expression and activity in this tissue. Overexpression of obscurin's rhoGEF domain and its effects on rhoA alter the expression of rho kinase and citron kinase, both of which can be activated by rhoA in other tissues. Injuries to rodent hindlimb muscles caused by large-strain lengthening contractions increases rhoA activity and displaces it from the M-bands to Z-disks, similar to the effects of overexpression of obscurin's rhoGEF domain. Our results suggest that obscurin's rhoGEF domain signals at least in part by inducing rhoA expression and activation, and altering the expression of downstream kinases in vitro and in vivo.

Full Text

Duke Authors

Cited Authors

  • Ford-Speelman, DL; Roche, JA; Bowman, AL; Bloch, RJ

Published Date

  • September 2009

Published In

Volume / Issue

  • 20 / 17

Start / End Page

  • 3905 - 3917

PubMed ID

  • 19605563

Pubmed Central ID

  • PMC2735489

Electronic International Standard Serial Number (EISSN)

  • 1939-4586

Digital Object Identifier (DOI)

  • 10.1091/mbc.e08-10-1029


  • eng

Conference Location

  • United States