Activation of dihydropyridine-sensitive parotid salivary gland calcium channels by epidermal growth factor.
The calcium channel complex of the parotid was isolated from solubilized acinar-cell membranes by affinity chromatography on wheatgerm agglutinin. The channel, after labelling the calcium antagonist-receptor site with [3H]-PN200-100, was reconstituted into phosphatidylcholine vesicles that exhibited active 45Ca2+ uptake. This uptake was independent of sodium and potassium gradients, indicating its electroneutrality. The channels responded in a dose-dependent manner to the dihydropyridine calcium antagonist, PN200-110, which at 0.4 microM exerted a maximal inhibitory effect of 75% on 45Ca2+ uptake; a 46% enhancement in 45Ca2+ uptake occurred with a specific calcium-channel activator, BAY K8644. On epidermal growth-factor (EGF) binding in the presence of ATP, there was an increase in tyrosine phosphorylation of 55 and 170 kDa calcium-channel proteins. Such phosphorylated channels, after reconstitution into vesicles, displayed a 61% greater 45Ca2+ uptake, indicating the involvement of tyrosine kinase in EGF-dependent activation of the calcium channel. The results point towards the importance of EGF in the regulation of calcium homeostasis in salivary gland.
Slomiany
B L
BL
Research Center, New Jersey Dental School, University of Medicine and Dentistry of New Jersey, Newark 07103-2400.
Fekete
Z
Z
Liu
J
J
Murty
V L
VL
Slomiany
A
A
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002132:Calcium Radioisotopes; D002462:Cell Membrane; D004095:Dihydropyridines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism; D017275:Isradipine / Q000378:metabolism / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D008081:Liposomes; D008297:Male; D010306:Parotid Gland / Q000166:cytology* / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D014443:Tyrosine / Q000378:metabolism
D015220:Calcium Channels; D002132:Calcium Radioisotopes; D004095:Dihydropyridines; D008081:Liposomes; D014443:Tyrosine; D004815:Epidermal Growth Factor; D007811:Lanthanum; C038806:1,4-dihydropyridine; D066246:ErbB Receptors; D002118:Calcium; D017275:Isradipine