Protein kinase c regulation of the adenylyl cyclase system in rat prostatic epithelium

Abstract

In the context of the crosstalk between transmembrane signalling pathways, we studied the loci within the stimulatory receptor/Gs protein/adenylyl cyclase system at which protein kinase C (PKC) exerts regulatory effects in rat prostatic epithelial cells. The treatment of cells with the PKC activator phorbol 12-myristate 13-acetate (PMA) resulted in an impairment of the stimulation of adenylyl cyclase activity in terms of both potency, as seen with both vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase-activating peptide (PACAP-27), and efficacy, as seen with the beta-adrenergic agonist isoproterenol. This inhibitory effect of PMA could be prevented by cell incubation with pertussis toxin but not with cholera toxin, pointing to a Gi- but not Gs-dependent mechanism. This hypothesis was reinforced by ADP-ribosylation experiments that showed a low extent of alpha i with pertussis toxin but no change of alpha s with cholera toxin, as well as by the observation of the loss of the ability of low Gpp[NH]p doses to inhibit forskolin-stimulated adenylyl cyclase activity (a measure of Gi function) after cell treatment with PMA. However, the phorbol ester did not modify the adenylyl cyclase catalytic subunit, as shown by experiments on direct stimulation of the enzyme by forskolin. Whatever the exact mechanisms, the results support a crosstalk between the PKC and the adenylyl cyclase systems in rat prostatic epithelial cells in terms of an impairment of adenylyl cyclase stimulation, due presumably to phosphorylation of both membrane receptors (coupled to Gs) and Gi protein, but not of Gs protein or the adenylyl cyclase itself.

Sympathetic Nerve Hyperactivity in the Spleen: Causal for Nonpathogenic-Driven Chronic Immune-Mediated Inflammatory Diseases (IMIDs)?

“…PKC also phosphorylates β 2 -ARs at the same site as PKA, thus, promoting receptor desensitization [ 176 , 182 , 183 ], but has reduced efficacy. PMA inhibits adenylyl cyclase activity [ 184 ], which limits cAMP production. In contrast, PKC suppresses GRK2 activity and promotes GRK2 trafficking to the membrane [ 185 , 186 , 187 ], events expected to suppress receptor desensitization and down-regulation.…”

Molecular Mechanisms Underlying β-Adrenergic Receptor-Mediated Cross-Talk between Sympathetic Neurons and Immune Cells

“…Like PKA, this kinase can directly phosphorylate the β 2 -AR to promote receptor desensitization, albeit with less efficacy than PKA [ 27 , 115 , 116 ]. Further, PMA-induced PKC impairs adenylyl cyclase activity in prostate cells stimulated with a β-AR agonist [ 117 ], an effect expected to reduce cAMP and thus, PKA production. PKC also inhibits the activity of GRK2 and promotes GRK2 translocation to the membrane [ 118 , 119 , 120 ], effects expected to promote receptor desensitization.…”

Constitutive activation of stimulatory guanine nucleotide binding protein (GSαQL)-mediated signaling increases invasiveness and tumorigenicity of PC-3M prostate cancer cells

“…Receptors for these ligands have also been localized within the prostate epithelium (Reubi, 1995;Wu et al, 1996;Killam et al, 1995;Gup et al, 1990;Lepor and Kuhar, 1984;Abdul et al, 1994;Carmena et al, 1995;Aprikian et al, 1996). Their mitogenic in¯uence on the neighboring cells is documented by the ®ndings that prostate cells in the vicinity of NE cells display increased expression of Bcl-2 and Ki-67 antigens (Segal et al, 1994;van Weerden et al, 1993).…”