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The inhibitory gamma subunit of the type 6 retinal cyclic guanosine monophosphate phosphodiesterase is a novel intermediate regulating p42/p44 mitogen-activated protein kinase signaling in human embryonic kidney 293 cells

Wan, K.F. and Sambi, B.S. and Frame, M.J. and Tate, R. and Pyne, N.J. (2001) The inhibitory gamma subunit of the type 6 retinal cyclic guanosine monophosphate phosphodiesterase is a novel intermediate regulating p42/p44 mitogen-activated protein kinase signaling in human embryonic kidney 293 cells. Journal of Biological Chemistry, 276 (41). pp. 37794-37802. ISSN 0021-9258

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Abstract

The inhibitory γ subunits of the retinal rod and cone photoreceptor type 6 retinal cyclic guanosine monophosphate phosphodiesterase (PDEγ) are expressed in non-retinal tissues. Here, we show that PDEγ interacts with the G-protein-coupled receptor kinase 2 signaling system to regulate the epidermal growth factor- and thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase in human embryonic kidney 293 cells. This is based upon several lines of evidence. First, the transfection of cells with an antisense rod PDEγ plasmid construct, which reduced endogenous rod PDEγ expression, ablated the epidermal growth factor- and thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase. Second, the transfection of cells with recombinant rod or cone PDEγ and/or G-protein-coupled receptor kinase 2 increased the stimulation of p42/p44 mitogen-activated protein kinase by epidermal growth factor or thrombin. In contrast, a G-protein-coupled receptor kinase 2 phosphorylation-resistant rod PDEγ mutant failed to increase the epidermal growth factor- or thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase and, in fact, functioned as a dominant negative. Thrombin also stimulated the association of endogenous rod PDEγ with dynamin II, which was increased in cells transfected with rod PDEγ or G-protein-coupled receptor kinase 2. Dynamin II plays a critical role in regulating endocytosis of receptor signal complexes required for activation of p42/p44 mitogen-activated protein kinase. Therefore, PDEγ may have an important role in promoting endocytosis of receptor signal complexes leading to the activation of p42/p44 mitogen-activated protein kinase. We conclude that PDEγ is an entirely novel intermediate regulating mitogenic signaling from both receptor tyrosine kinase and G-protein-coupled receptors in human embryonic kidney 293 cells.