FIGURE 20-39 The dystrophin glycoprotein complex (DGC) in skeletal muscle cells. This schematic model shows that the DGC comprises three subcomplexes: the α, β dystroglycan subcomplex; the sarcoglycan/sarcospan subcomplex of integral membrane proteins; and the cytosolic adapter subcomplex comprising dystrophin, other adapter proteins, and signaling molecules. Through its O-linked matriglycan sugars (see Figure 20-30c), α-dystroglycan binds to components of the basal lamina, such as laminin and perlecan, and to cell-surface proteins, such as neurexin in neurons. Dystrophin—the protein that is defective in Duchenne muscular dystrophy—links β-dystroglycan to the actin cytoskeleton, and α-dystrobrevin links dystrophin to the sarcoglycan/sarcospan subcomplex. Nitric oxide synthase (NOS) produces nitric oxide, a gaseous signaling molecule, and GRB2 is a component of signaling pathways activated by certain cell-surface receptors (see Chapter 15). See S. J. Winder, 2001, Trends Biochem. Sci. 26:118; D. E. Michele and K. P. Campbell, 2003, J. Biol. Chem. 278(18):15457–15460; and T. Yoshida-Moriguchi and K. P. Campbell, 2015, Glycobiology 25:702–713.