Immunohistochemical and Immunocytochemical Localization of Cathepsin E Compared with Cathepsin D
Recent reports have suggested that cathepsin E is a non-lysosomal aspartic proteinase and that this enzyme participates in extralysosomal proteolysis.1–3 Although its enzymatic and structural properties have been demonstrated,4–7 its physiological function is still unknown. Although cathepsin E can be clearly distinguished from another intracellular aspartic proteinase cathepsin D,8–10 the functional relationship between the two enzymes remains to be answered. Recently, the distribution of cathepsins E and D has been shown to be markedly different in various rat tissues and cells by immunochemical analyses employing discriminative antibodies specific for each enzyme. The results indicated that cathepsin D has a ubiquitous distribution, while cathepsin E has a relatively limited distribution. Of the cell types tested, gastrointestinal tracts, lymphoid tissues, urinary tracts and blood cells contained high levels of cathepsin E. The other rat tissues had little or no detectable cathepsin E. The stomach is one of the most interesting organs, because the greatest accumulation of cathepsin E is observed in the gastric mucosa1,11 and because this tissue contains not only a non-secretory type of aspartic proteinases (cathepsins E and D) but also a secretory type of the enzymes (pepsin, gastricsin etc.). In order to clarify the functional characteristics of cathepsin E in human stomach, we have examined the intracellular localization of cathepsin E in a variety of physiological and pathological processes, as compared with that of cathepsin D, by immunohistochemical and immunocytochemical analyses using the antibodies specific for each enzyme.
KeywordsAdenocarcinoma Cytosol Hematoxylin Kato
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- 12.T. Saku, H. Sakai, Y. Shibata, Y. Kato and K. Yamamoto, J. Biochem. in press.Google Scholar