Epidermal growth factor binding and stimulation of inositol trisphosphate production in basolateral membranes from dog kidney.
To ascertain whether epidermal growth factor (EGF) receptors are present in proximal tubular basolateral membranes from dog kidney and whether the growth factor activates phospholipase C at this site, we measured binding of 125I-EGF in isolated membranes and determined whether incubation of the membranes with EGF results in generation of inositol trisphosphate. Specific binding of 125I-EGF to basolateral membranes was observed that was half-maximally inhibited by approximately 7 x 10(-10) M EGF. The specific binding capacity of basolateral membranes for EGF averaged 45.9 fmol/mg protein. 125I-EGF was crosslinked to 2 proteins in basolateral membranes with M(r)s of 170,000 and 150,000. EGF stimulated phosphorylation of a 170,000 M(r) protein. Incubation of basolateral membranes with EGF stimulated inositol trisphosphate production in a concentration-dependent manner. We conclude that EGF activates a phospholipase C activity that cleaves phosphatidylinositol 4,5-bisphosphate within the basolateral membrane.
Rogers
S A
SA
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Hammerman
M R
MR
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism
D004815:Epidermal Growth Factor; D015544:Inositol 1,4,5-Trisphosphate; D066246:ErbB Receptors; D010738:Type C Phospholipases