740403.fig.001a
(a)
740403.fig.001b
(b)
Figure 1: (a) Molecular structure of DGC (traditional type), present in Cajal cytoplasmic band of myelinated Schwann cells. a- and b-dystroglycan form membrane-spanning complex in Schwann cell abaxonal membrane. Mucin-like domain of a-dystroglycan is involved in the interaction with laminin via laminin G-like domains. a-dystroglycan is noncovalently anchored to b-dystroglycan. The cytoplasmic tail of b-dystrogylcan is anchored to the cytoskeletal proteins, Dp116, Schwann cell-specific isoform of dystrophin, or utrophin, an autosomal homolog of dystrophin. Utrophin interact with f-actin at the N-teminus. Utrophin or Dp116 interacts with syntrophins (a1, b1, b2, g2) and a-dystrobrevin-1. Also at least four isoforms of sarcoglycan (b, d, e, z) form sarcoglycan complex in abaxonal membrane and interact with dystroglycan complex. Sarcospan is supposed to interact with sarcoglycan complex. Thus DGC provides the physical link between extracellular matrix and submembranous cytoskeleton in Schwann cells. (b) Molecular framework of DGC present in membrane portion directly apposed to myelin sheath (DRP2/periaxin rich plaque) of myelinated Schwann cells. In DRP2/periaxin rich plaques, dystroglycan complex intracellularly interact with DRP2, third member of dystrophin family, and periaxin, homodimeric PDZ domain-containing protein, via cytoplasmic domain of b-dystroglycan. This type of DGC lacks syntrophins and dystrobrevin.