Release of renal dipeptidase from glycosylphosphatidylinositol anchor by insulin-triggered phospholipase C/intracellular Ca2+.
Glycosylphosphatidylinositol (GPI) anchored proteins appear to be released from the plasma membrane due to various extracellular stimuli. To determine the signaling pathway from insulin to GPI-protein, the release of GPI-renal dipeptidase (RDPase, EC 3.4.13.19) from porcine proximal tubules, stimulated by insulin, was explored. Insulin stimulated the release of RDPase in a concentration-dependent manner (half maximal release at 0.58 nM), which peaked at 10-20 min. Western blot analysis, with antibody against the cross-reacting determinant (CRD), revealed that RDPase was released by a GPI-specific phospholipase C (GPI-PLC), and was shown to be Ca2+-dependent. A PI-PLC inhibitor, U73122, effectively blocked the effect of insulin on the release of RDPase, suggesting insulin is associated with an intracellular PI-PLC. Insulin treatment increased the production of intracellular Ca2+ from porcine proximal tubules. Intracellular Ca2+, coupled with insulin, facilitated the releases of RDPase, an inhibitor of inositol trisphosphate-dependent Ca2+ from the endoplasmic reticulum, and a Ca2+ channel blocker that blocked the effect of insulin. Taken together, these results suggest that insulin, in part, may activate a GPI-PLC, via PI-PLC/intracellular Ca2+, which may consequently stimulate the release of RDPase.
Yoon
Hyun Joong
HJ
College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju 500-757, Korea.
Park
Sung Wook
SW
Lee
Hwanghee Blaise
HB
Im
Shun Young
SY
Hooper
Nigel M
NM
Park
Haeng Soon
HS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004150:Dipeptidases / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000201:enzymology*; D013552:Swine; D010738:Type C Phospholipases / Q000502:physiology*
D017261:Glycosylphosphatidylinositols; D007328:Insulin; D010738:Type C Phospholipases; D004150:Dipeptidases; C038937:dipeptidase; D002118:Calcium