Expression of lysosomal-related proteins and their gene in the skeletal muscles of distal myopathy with rimmed vacuoles

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Investigators have speculated that the degenerative process in distal myopathy with rimmed vacuoles (DMRV) mainly involves the lysosomal system. To investigate possible protein or gene abnormalities related to intracellular lysosomal proteolytic pathways in DMRV-affected muscles, we performed immunohistochemical analyses of certain proteins in muscle biopsy specimens obtained from patients with various neuromuscular diseases including DMRV.Abnormal increases in clathrin, adaptin (AP-1 and AP-2), Golgi zone protein were demonstrated in DMRV muscles as compared with normal and diseased controls. These proteins were often observed inside or on the rims of vacuoles and in the cytoplasm of vacuolated fibers as well as atrophic fibers and necrotic fibers. The rims of rimmed vacuoles were negative for kinectin, an endoplasmic reticulum-binding protein, Positive staining for this protein, however, was sometimes seen inside the vacuoles in DMRV-affected fibers. These results suggest increased e … More ndocytosis at the plasma membrane as well as secretion involving transport from the trans-Golgi network of the Golgi apparatus in DMRV.Accumulation of various lysosome-related proteins within the rimnmed vacuoles indicates at least some of these vacuoles may be autolysosomes.Abnormal increases in clathrin, adaptin (AP-1 and AP-2), Golgi zone protein were demonstrated in DMRV muscles as compared with normal and diseased controls. These proteins were often observed inside or on the rims of vacuoles and in the cytoplasm of vacuolated fibers as well as atrophic fibers and necrotic fibers. The rims of rimmed vacuoles were negative for kinectin, an endoplasmic reticulum-binding protein. Positive staining for this protein, however, was sometimes seen inside the vacuoles in DMRV-affected fibers. These results suggest increased endocytosis at the plasma membrane as well as secretion involving transport from the trans-Golgi network of the Golgi apparatus in DMRV.Accumulation of various lysosome-related proteins within the rimmed vacuoles indicates at least some of these vacuoles may be autolysosomes.We also measured the levels of mRNA for lysosome-related proteins in the denervated and innervated soleus muscles from saline- and chloroquine-treated rats using the Northern blot. The denervated muscle of chloroquine-treated rats is known as an animal model of human DMRV.These protein mRNA levels, especially mannose-6-phospate receptor mRNA, were significantly elevated in denervated muscles from chloroquine-treated rats as compared with innervated muscles of both experimental rats and denervated muscle from saline-treated rats. These levels were higher on day 4 than on days 1,2, and 8. The accumulation of rimmed vacuoles-like autophagic vacuoles was marked only in chloroquine-treated muscles after denervation, especially on day 8. This result suggests that lysosomal system, autophagic vacuole formation derived from endoplasmic reticulum and early endosome (primary lysosome) formation from trans-Golgi network, is markedly activated in the myopathies with rimmed vacuoles or autophagic vacuoles such as DMRV. Less