Selective localization of calpain I (the low-Ca2+-requiring form of Ca2+-dependent cysteine proteinase) in B-cells of human pancreatic islets.
An immunohistochemical study was performed to localize two distinct Ca2+-proteases (low-Ca2+-requiring calpain I and high-Ca2+-requiring calpain II) and their specific inhibitor (calpastatin) in human pancreas using the respective monospecific antibodies. Strongly positive staining by anti-calpain I antibody was found in pancreatic islets, specifically in B-cells, whereas the exocrine pancreatic tissue showed essentially no positive immunostaining. No such specific staining was found with anti-calpain II antibodies or anti-calpastatin antibodies. The results suggest that the Ca2+-dependent proteolysis in B-cells can be triggered by a small rise of the intracellular Ca2+ concentration without serious interference by the endogenous inhibitor.
Kitahara
A
A
Ohtsuki
H
H
Kirihata
Y
Y
Yamagata
Y
Y
Takano
E
E
Kannagi
R
R
Murachi
T
T
D002118:Calcium / Q000502:physiology; D002154:Calpain; D010450:Endopeptidases / Q000032:analysis* / Q000276:immunology; D006651:Histocytochemistry; D006801:Humans; D007515:Islets of Langerhans / Q000201:enzymology*; D011493:Protein Kinase C; D011494:Protein Kinases / Q000032:analysis
D011494:Protein Kinases; D011493:Protein Kinase C; D010450:Endopeptidases; D002154:Calpain; D002118:Calcium