The 8th and 9th tandem spectrin-like repeats of utrophin cooperatively form a functional unit to interact with polarity-regulating kinase PAR-1b.
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.
Yamashita
Kazunari
K
Department of Molecular Biology, Yokohama City University Graduate School of Medical Science, 3-9 Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan.
Suzuki
Atsushi
A
Satoh
Yoshinori
Y
Ide
Mariko
M
Amano
Yoshiko
Y
Masuda-Hirata
Maki
M
Hayashi
Yukiko K
YK
Hamada
Keisuke
K
Ogata
Kazuhiro
K
Ohno
Shigeo
S
D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004285:Dogs; D049030:Dystroglycans / Q000378:metabolism; D016189:Dystrophin / Q000378:metabolism; D006801:Humans; D018482:Muscle, Skeletal / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D012508:Sarcolemma / Q000378:metabolism; D012694:Serine / Q000235:genetics / Q000378:metabolism; D013049:Spectrin / Q000378:metabolism; D020080:Tandem Repeat Sequences / Q000235:genetics; D049411:Utrophin / Q000235:genetics / Q000378:metabolism*
D016189:Dystrophin; C483599:UTRN protein, human; D049411:Utrophin; D013049:Spectrin; D049030:Dystroglycans; D012694:Serine; C094670:MARK2 protein, human; D017346:Protein Serine-Threonine Kinases