title: The Src signaling pathway regulates osteoclast lysosomal enzyme secretion and is rapidly modulated by estrogen.
abstract: To investigate the role of the pp60src signaling pathway in osteoclast activity, we have used dominant negative pp60src, c-ras, and c-raf expression vectors to individually disrupt their functions in osteoclasts. Osteoclasts were transiently transfected and secretions of cathepsin B/K and tartrate-resistant acid phosphatase (TRAP) were monitored. Expression of these constructs increased secretion of lysosomal enzymes. In contrast, constitutively active pp60src expression caused decreased lysosomal enzyme secretion. Osteoclasts respond to 17-beta estradiol (17betaE2) treatment with decreased lysosomal enzyme secretion. Therefore, we investigated the effects of E2 on pp60src kinase activity and observed an E2 time- and dose-dependent decrease in cytoskeletal membrane-associated pp60src tyrosine kinase activity. We have shown that estrogen decreases lysosomal enzyme gene expression and secretion; so we have examined the effects of the expression constructs on estrogen regulation of enzyme secretion. Constitutively active pp60src blocked E2 effects on secretion whereas expression of dominant negative pp60src, c-Ras, or c-Raf enhanced E2 effects. These data support that the kinase domain of cytoskeletal-associated pp60src is likely to be involved in the regulation of lysosomal enzyme secretion.
authors.affiliation: Department of Biology, University of Minnesota, Duluth 55812, USA.
authors.forename: D
authors.initials: D
authors.lastname: Pascoe
authors.forename: M J
authors.initials: MJ
authors.lastname: Oursler
mesh_terms: D000135:Acid Phosphatase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002401:Cathepsin B / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002645:Chickens; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism* / Q000494:pharmacology; D000077267:Fulvestrant; D011905:Genes, ras; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology*; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D019908:Proto-Oncogene Proteins c-raf / Q000187:drug effects / Q000378:metabolism; D051575:Proto-Oncogene Proteins c-yes; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000071681:Tartrate-Resistant Acid Phosphatase; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D004965:Estrogen Antagonists; D004967:Estrogens; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D000077267:Fulvestrant; D004958:Estradiol; D051076:Proto-Oncogene Proteins c-fyn; D051575:Proto-Oncogene Proteins c-yes; D016392:Proto-Oncogene Proteins pp60(c-src); D019061:src-Family Kinases; D019908:Proto-Oncogene Proteins c-raf; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D002401:Cathepsin B