Activation of gastric mucosal calcium channels by epidermal growth factor.
1. Gastric mucosal calcium channel complex was isolated from the solubilized epithelial cell membranes by affinity chromatography on wheat germ agglutinin. 2. The complex following labeling with [3H]PN200-110 was reconstituted into phosphatidylcholine vesicles which exhibited active 45Ca2+ uptake into intravesicular space as evidenced by La3+ displacement and osmolarity measurements. The 45Ca2+ uptake was independent of sodium and potassium gradients indicating the electroneutral nature of the process. 3. The gastric mucosal channels on epidermal growth factor binding in the presence of ATP responded by an increase in protein tyrosine phosphorylation of 55 and 170 kDa subunits of calcium channel. 4. The phosphorylated channels following reconstitution into vesicles displayed at 48% greater 45Ca2+ uptake, thus indicating the tyrosine kinase involvement in EGF dependent activation of calcium channel. 5. The results point towards the importance of epidermal growth factor in the maintenance of gastric mucosal calcium homeostasis.
Liu
J
J
Research Center, New Jersey Dental School, University of Medicine and Dentistry of New Jersey, Newark 07103-2400.
Fekete
Z
Z
Slomiany
A
A
Slomiany
B L
BL
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002132:Calcium Radioisotopes; D002846:Chromatography, Affinity; D004095:Dihydropyridines / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D017275:Isradipine; D008297:Male; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D014316:Tritium
D015220:Calcium Channels; D002132:Calcium Radioisotopes; D004095:Dihydropyridines; D014316:Tritium; D004815:Epidermal Growth Factor; C038806:1,4-dihydropyridine; D002118:Calcium; D017275:Isradipine