Lysosomal-autophagic system

Lysosomes are subcellular organelles in which a wide range of catabolic enzymes are stored in a closed, protective membrane system. They are major sites of intracellular digestion of complex macromolecules derived from both intracellular (autophagic) and extracellular (het-erophagic) sources. Lysosomal enzymes show optimal activity at acidic pH. The pattern of enzymes in lysosomes may depend upon the tissue of origin, as well as upon the physiological or developmental state of the cells. 

In addition to activated macroautophagy, our studies provided important evidence that autophagy related to lysosomal function is impaired in s-IBM muscle fibers. They showed a decrease of lysosomal cathepsin D and B enzymatic activities that appeared spedfic to s-IBM, because in polymyositis muscle fibers their activities were actually increased in our study [13] and in studies by others (referenced in [13]). In polymyositis macroautophagy was also increased but autophagic vacuoles and indusions do not form, perhaps because the lysosomal system may be functioning adequately. Our results also suggest that lymphocytic inflammation, which is... 

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