The 8th and 9th tandem spectrin-like repeats of utrophin cooperatively form a functional unit to interact with polarity-regulating kinase PAR-1b

Biochem Biophys Res Commun. 2010 Jan 1;391(1):812-7. doi: 10.1016/j.bbrc.2009.11.144. Epub 2009 Nov 27.


Utrophin is a widely expressed paralogue of dystrophin, the protein responsible for Duchenne muscular dystrophy. Utrophin is a large spectrin-like protein whose C-terminal domain mediates anchorage to a laminin receptor, dystroglycan (DG). The rod domain, composed of 22 spectrin-like repeats, connects the N-terminal actin-binding domain and the C-terminal DG binding domain, and thus mediates molecular linkage between intracellular F-actin and extracellular basement membrane. Previously, we demonstrated that a cell polarity-regulating kinase, PAR-1b, interacts with the utrophin-DG complex, and positively regulates the interaction between utrophin and DG. In this study, we demonstrate that the 8th and 9th spectrin-like repeats (R8 and R9) of utrophin cooperatively form a PAR-1b-interacting domain, and that Ser1258 within R9 is specifically phosphorylated by PAR-1b. Substitution of Ser1258 to alanine reduces the interaction between utrophin and DG, suggesting that the Ser1258 phosphorylation contributes to the stabilization of the utrophin-DG complex. Interestingly, PAR-1b also binds and phosphorylates R8-9 of dystrophin, and colocalizes with dystrophin at the skeletal muscle membrane. These results reveal a novel function of the rod domain of utrophin beyond that of a passive structural linker connecting the N- and C-terminal domain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Binding Sites
  • Cell Line
  • Dogs
  • Dystroglycans / metabolism
  • Dystrophin / metabolism
  • Humans
  • Muscle, Skeletal / metabolism*
  • Phosphorylation
  • Protein Serine-Threonine Kinases / metabolism*
  • Repetitive Sequences, Amino Acid / genetics
  • Sarcolemma / metabolism
  • Serine / genetics
  • Serine / metabolism
  • Spectrin / metabolism
  • Tandem Repeat Sequences / genetics
  • Utrophin / genetics
  • Utrophin / metabolism*


  • Dystrophin
  • UTRN protein, human
  • Utrophin
  • Spectrin
  • Dystroglycans
  • Serine
  • MARK2 protein, human
  • Protein Serine-Threonine Kinases