Cysteine string protein expression in mammary epithelial cells.
Cysteine string protein (Csp) is a secretory vesicle protein previously demonstrated to be required for Ca2+-regulated exocytosis in neurons and endocrine cells. It has been suggested to function by regulating voltage-gated Ca2+ channels or, alternatively, to have a more direct effect on the regulated exocytotic machinery. Here we demonstrate the expression of Csp in mammary epithelial cells and in the KIM-2 mammary cell line. In KIM-2 cells, Csp was found to be associated with a population of small vesicles and showed partial co-distribution with the vesicle protein cellubrevin. KIM-2 cells do not express detectable levels of voltage-gated Ca2+ channels, ruling these out as a site of action. Using the release of transfected growth hormone (GH) as an assay of secretion, we found that GH is secreted in an exclusively constitutive manner from KIM-2 cells. Overexpression of Csp1 inhibits regulated exocytosis in other cell types but has no effect on constitutive GH release by KIM-2 cells. These results suggest that Csp does not have a major function in constitutive exocytosis.
Gleave
T L
TL
The Physiological Laboratory, University of Liverpool, UK.
Beechey
R B
RB
Burgoyne
R D
RD
D000818:Animals; D016375:Antisense Elements (Genetics); D002461:Cell Line, Transformed; D004847:Epithelial Cells / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology; D005260:Female; D015870:Gene Expression / Q000502:physiology; D013006:Growth Hormone / Q000235:genetics / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins; D007774:Lactation / Q000502:physiology; D008321:Mammary Glands, Animal / Q000166:cytology; D008564:Membrane Potentials / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D018408:Patch-Clamp Techniques; D021381:Protein Transport / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D022142:Secretory Vesicles / Q000378:metabolism; D014162:Transfection; D051040:Vesicle-Associated Membrane Protein 3
D016375:Antisense Elements (Genetics); D050956:HSP40 Heat-Shock Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D051040:Vesicle-Associated Membrane Protein 3; C088460:cysteine string protein; D013006:Growth Hormone