T. Mitsui et al., Functional association between nicotinic acetylcholine receptor and sarcomeric proteins via actin and desmin filaments, J CELL BIOC, 77(4), 2000, pp. 584-595
By affinity chromatography utilizing alpha-cobrotoxin from digitonin-solubi
lized fractions of rabbit skeletal muscle, we found that many proteins are
associated with the nicotinic acetylcholine receptor (AChR). In addition to
the proteins we previously reported to bind to AChR (including dystrophin-
dystrophin-associated protein (DAP) complex, utrophin, rapsyn, and actin; M
itsui et at. [1996] Biochem. Biophys. Res. Commun.224:802-807), alpha-actin
in, desmin, myosin, tropomyosin, troponin T, and titin are also identified
to be associated with AChR. Alkaline treatment or Triton X-100 solubilizati
on released dystrophin-DAP complex, utrophin, and rapsyn from the AChR frac
tion, while actin and desmin remained associated. These findings demonstrat
e that AChR is supported primarily by a submembranous organization of actin
and desmin filaments, and is linked to sarcomeric proteins via these filam
ents. To Further investigate whether the association has any functional rol
e, we studied the effect of acetylcoline on ATPase activity of the AChR fra
ction. Acetylcholine (0.5-4 mu M) significantly activated Mg2+-ATPase activ
ity of digitonin-solubilized AChR fraction (P < 0.05). Furthermore, we foun
d that desmin as well as actin activated myosin Mg2+-ATPase activity. From
these findings, it is suggested that desmin and actin form a submembranous
organization in the postsynaptic region, and function as mediators of excit
ation of AChR to the sarcomeric contraction system, J. Cell. Biochem. 77: 5
84-595,2000. (C) 2000 Wiley-Liss, Inc.