Pertussis toxin induces parallel loss of neuropeptide Y Y1 receptor dimers and Gi alpha subunit function in CHO cells.
Treatment with pertussis toxin in addition to a stable inhibition of G(i)alpha subunits of G-proteins also strongly reduced human neuropeptide Y Y(1) receptors expressed in Chinese hamster ovary (CHO) cells. This was reflected in abolition of the inhibition by Y(1) agonists of forskolin-stimulated adenylyl cyclase in intact cells, and of Y(1) agonist stimulation of GTPgammaS binding to particulates from disrupted cells. The loss of both receptor and G(i)alpha subunit function was attenuated by ammonium chloride, an inhibitor of acid proteinases, pointing to a chaperoning co-protection of active pertussis toxin-sensitive Galpha subunits and Y(1) receptors. The surface complement of the Y(1) receptor was changed a little in conditions of approximately 85% decrease of the Y(1) population, but the rate of the Y(1) receptor-linked internalization of agonist peptides was reduced about 70%. The preserved receptor fraction consisted of monomers significantly coupled to G(q)alpha subunits. The persistent pertussis toxin-insensitive internalization of agonists with the Y(1) receptor may reflect a rescue or alternative switching that could be important for cell functioning in neuropeptide Y-rich environments. The results are compatible with a loss, due to G(i)alpha subunit inactivation by the toxin, of a large Y(1) receptor reserve constituted of oligomers associating with heterotrimeric G-proteins.
Parker
Steven L
SL
Department of Pharmacology, University of Tennessee Health Science Center, Memphis, TN 38163, USA. slparker@utmem.edu
Parker
Michael S
MS
Sah
Renu
R
Balasubramaniam
Ambikaipakan
A
Sallee
Floyd R
FR
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D005576:Colforsin; D006224:Cricetinae; D003412:Cricetulus; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000187:drug effects* / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006801:Humans; D037342:Pertussis Toxin / Q000494:pharmacology*; D051381:Rats; D017476:Receptors, Neuropeptide Y / Q000187:drug effects* / Q000378:metabolism; D013552:Swine
D017476:Receptors, Neuropeptide Y; C097212:neuropeptide Y-Y1 receptor; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D000262:Adenylyl Cyclases