The sarcoglycan complex in Schwann cells and its role in myelin stability.

Sarcoglycans are originally identified in muscle for their involvement in limb-girdle muscular dystrophies. They form a multi-meric complex (alpha-, beta-, gamma-, delta-sarcoglycan) that associates with dystrophin, dystroglycan and other proteins to constitute the larger dystrophin-glycoprotein complex at the muscle membrane. Three sarcoglycan subunits (epsilon-, beta-, delta-sarcoglycan) were previously identified in Schwann cells and shown to associate with dystroglycan and a Schwann cell-specific dystrophin isoform (Dp116) at the outermost Schwann cell membrane.

The 16 kDa subunit of vacuolar H+-ATPase is a novel sarcoglycan-interacting protein.

The sarcoglycan complex in muscle consists of alpha-, beta-, gamma- and delta-sarcoglycan and is part of the larger dystrophin-glycoprotein complex (DGC), which is essential for maintaining muscle membrane integrity. Mutations in any of the four sarcoglycans cause limb-girdle muscular dystrophies (LGMD). In this report, we have identified a novel interaction between delta-sarcoglycan and the 16 kDa subunit c (16K) of vacuolar H(+)-ATPase.

Identification of functional domains in sarcoglycans essential for their interaction and plasma membrane targeting.

Mutations in sarcoglycans have been reported to cause autosomal-recessive limb-girdle muscular dystrophies. In skeletal and cardiac muscle, sarcoglycans are assembled into a complex on the sarcolemma from four subunits (alpha, beta, gamma, delta). In this report, we present a detailed structural analysis of sarcoglycans using deletion study, limited proteolysis and co-immunoprecipitation.

Phospholemman overexpression inhibits Na+-K+-ATPase in adult rat cardiac myocytes: relevance to decreased Na+ pump activity in postinfarction myocytes.

Messenger RNA levels of phospholemman (PLM), a member of the FXYD family of small single-span membrane proteins with putative ion-transport regulatory properties, were increased in postmyocardial infarction (MI) rat myocytes. We tested the hypothesis that the previously observed reduction in Na+-K+-ATPase activity in MI rat myocytes was due to PLM overexpression. In rat hearts harvested 3 and 7 days post-MI, PLM protein expression was increased by two- and fourfold, respectively.

Specific assembly pathway of sarcoglycans is dependent on beta- and delta-sarcoglycan.

Mutations in sarcoglycans (SG) have been reported to cause autosomal-recessive limb-girdle muscular dystrophy (LGMD) and dilated cardiomyopathy. In skeletal and cardiac muscle, sarcoglycans exist as a complex of four transmembrane proteins (alpha-, beta-, gamma-, and delta-SG). In this study, the assembly of the sarcoglycan complex was examined in a heterologous expression system.

Long-term persistence of donor nuclei in a Duchenne muscular dystrophy patient receiving bone marrow transplantation.

Duchenne muscular dystrophy (DMD) is a severe progressive muscle-wasting disorder caused by mutations in the dystrophin gene. Studies have shown that bone marrow cells transplanted into lethally irradiated mdx mice, the mouse model of DMD, can become part of skeletal muscle myofibers. Whether human marrow cells also have this ability is unknown.

Erythropoietin modulates calcium influx through TRPC2.

Mammalian isoforms of calcium-permeable Drosophila transient receptor potential channels (TRPC) are involved in the sustained phase of calcium entry in nonexcitable cells. Erythropoietin (Epo) stimulates a rise in intracellular calcium ([Ca](i)) via activation of voltage-independent calcium channel(s) in erythroid cells. Here, involvement of murine orthologs of classical TRPC in the Epo-modulated increase in [Ca](i) was examined.