Naslov
Heapotcyte growth factor activates phosphoinositide 3-kinase C2beta in renal brush-border plasma membranes
(Hepatocyte growth factor activates phosphoinositide 3-kinase C2beta in renal brush-border plasma membranes)

Autori
Crljen, Vladiana ; Volinia, Stefano ; Banfić, Hrvoje

Izvornik
Biochemical Journal (0264-6021) 365 (2002), 3; 791-799

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
calpain; phosphatidylinositide; phospholipase C

Sažetak
Upon stimulation of renal cortical slices with heapatocyte growth factor (HGF), inositol lipid metabolism was studied in basal-lateral plasma membranes (BLM) and brush-border plasma membranes (BBM). Whereas in BLM rapid increases in 1, 2-diacylglycerol, PtdIns(3, 4, 5)P_3 and PtdIns(3, 4)P_2 were observed, suggesting that in BLM HGF activates both phospholipase C (PLC) and phosphoinositide 3-kinase (PI3K), in BBM only HGF-induced transient accumulation of PtdIns3P was seen, which was temporarily delayed from signalling events in BLM and could be blocked by the PtdIns-specific-PLC inhibitor ET18-OCH_3 and the calpain inhibitor calpeptin, suggesting that 3-kinase activation in BBM lies downstream of PLC activation in BLM and is a calpain-mediated event. Moreover, the increase in immunoprecipitable PI3K-C2beta activity, which is sensitive to wortmannin (10 nM) and shows strong preference for PtdIns over PtdIns4P as a substrate, was observed only in BBM upon stimulation of renal cortical slices with HGF and could be mimicked by the Ca^2^+ ionophore A23187 and blocked by the cell-penetrant Ca^2^+ chelator BAPTA-AM [1, 2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetra-acetic acid tetrakis-(acetoxymethyl ester)]. On Western blots PI3K-C2beta revealed a single immunoreactive band of 180 kDa in BLM and BBM, while after stimulation with HGF a gel shift of 18 kDa was noticed only in BBM, suggesting that the observed enzyme activation is achived by proteolysis. When BBM were subjected to short-term (15 min) exposure to mu-calpain, a similar gel-shift together with an increase in PI3K-C2beta activity was observed, when compared with the BBM harvested after HGF stimulation. The above-mentioned gel shift and increase in PI3K-C2beta activity could be prevented by calpain inhibitor calpeptin. The data presented in this report show in renal cells there is a spatial separation of the inositol lipid signalling system between BLM and BBM, and that HGF causes activation of PLC and PI3K primarily in BLM, which leads to calpain-mediated activation of PI3K-C2beta in BBM with concomitant increase in PtdIns3P.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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