Transduction proteins of olfactory receptor cells: identification of guanine nucleotide binding proteins and protein kinase C

Biochemistry ◽  
1987 ◽  
Vol 26 (3) ◽  
pp. 788-795 ◽  
Author(s):  
Robert R. H. Anholt ◽  
Susanne M. Mumby ◽  
Doris A. Stoffers ◽  
Peggy R. Girard ◽  
J. F. Kuo ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Olfactory Receptor ◽  
Guanine Nucleotide ◽  
Olfactory Receptor Cells ◽  
Receptor Cells ◽  
Kinase C ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Proteins ◽  
Guanine Nucleotide Binding Proteins

scholarly journals Okadaic acid identifies a phosphorylation/dephosphorylation cycle controlling the inhibitory guanine-nucleotide-binding regulatory protein Gi2

1991 ◽  
Vol 274 (2) ◽  
pp. 317-321 ◽  
Author(s):  
M Bushfield ◽  
B E Lavan ◽  
M D Houslay
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Okadaic Acid ◽  
Regulatory Protein ◽  
Nucleotide Binding ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Kinase C ◽  
Guanine Nucleotide Binding

Recently, the alpha-subunit of the inhibitory guanine-nucleotide-binding protein Gi2 (alpha-Gi2) has been shown to be a substrate for phosphorylation both by protein kinase C and also by other unidentified kinase(s) which are activated as a result of elevated cyclic AMP levels in intact rat hepatocytes [Bushfield, Murphy, Lavan, Parker, Hruby, Milligan & Houslay (1990) Biochem. J. 268, 449-457]. Here we show that the incorporation of [32P]Pi into alpha-Gi2 was enhanced 3-fold by incubation of intact hepatocytes with the tumour promoter and protein phosphatase (1 and 2A) inhibitor, okadaic acid. This action was both time- and concentration-dependent and was accompanied by a loss of guanine-nucleotide-induced inhibition of adenylate cyclase. The increased labelling of alpha-Gi2 induced by okadaic acid was partially additive with that elicited by 8-bromo cyclic AMP, but not with that elicited by the protein kinase C activator phorbol 12-myristate 13-acetate. We suggest that, in the absence of hormones, the activity of alpha-Gi2 is under the control of a dynamic phosphorylation/dephosphorylation system involving protein kinase C and protein phosphatases 1 and/or 2A. This highlights the regulation of kinases and phosphatases as both providing potentially important mechanisms for causing ‘cross-talk’ between different signalling systems, in this instance controlling cellular responsiveness through regulation of alpha-Gi2 phosphorylation.

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