TYROSINE PROTEIN-PHOSPHORYLATION IN PLASMA-MEMBRANES OF RAT-KIDNEY CORTEX

Citation
L. Tremblay et R. Beliveau, TYROSINE PROTEIN-PHOSPHORYLATION IN PLASMA-MEMBRANES OF RAT-KIDNEY CORTEX, The American journal of physiology, 267(3), 1994, pp. 60000415-60000422
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physiology
ISSN journal
0002-9513
Volume
267
Issue
3
Year of publication
1994
Part
2
Pages
60000415 - 60000422
Database
ISI
SICI code
0002-9513(1994)267:3<60000415:TPIPOR>2.0.ZU;2-1
Abstract
The endogenous tyrosine protein kinase activity (TPKA) associated with brush-border (BBM) and basolateral (BLM) membranes of rat kidney cort ex was studied with an anti-phosphotyrosine monoclonal antibody (PY20) . Distinct major phosphotyrosine-containing proteins were associated w ith BBM (50, 54, and 120 kDa) and BLM (37, 90, 130, and 170 kDa). For both plasma membranes, tyrosine phosphorylation leveled off after 10 m in of incubation. Endogenous phosphotyrosine-specific protein phosphat ases (PTPases) were active in both membranes, since the presence of so dium vanadate or ammonium molybdate, which are inhibitors of PTPases, was essential to detect endogenous phosphorylation. Substrates and/or tyrosine protein kinases (TPKs) seem to be differently distributed in these plasma membranes, since phosphorylation of endogenous substrates in BLM and BBM was differently sensitive to competitive inhibitors of TPKs. Moreover, insulin- and insulin-like growth factor I-stimulated tyrosine phosphorylation of a 90-kDa substrate was only observed in so lubilized BLM proteins. However, similar p60(v-src)-related TPKs appea r to be present in the BBM and BLM, since an antibody raised against p 60(v-src) recognized proteins of 52, 58, and 75 kDa by immunoblotting and could immunoprecipitate the TPKs associated with both plasma membr anes. These data provide evidence that the endogenous tyrosine protein phosphorylation observed in the ELM is catalyzed by nonreceptor TPKs as well as receptor TPKs, whereas that observed in the BBM is exclusiv ely due to nonreceptor TPKs.