Current biology : CB
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Current biology : CB · Feb 2001
Two RGS proteins that inhibit Galpha(o) and Galpha(q) signaling in C. elegans neurons require a Gbeta(5)-like subunit for function.
Gbeta proteins have traditionally been thought to complex with Ggamma proteins to function as subunits of G protein heterotrimers. The divergent Gbeta(5) protein, however, can bind either Ggamma proteins or regulator of G protein signaling (RGS) proteins that contain a G gamma-like (GGL) domain. RGS proteins inhibit G protein signaling by acting as Galpha GTPase activators. While Gbeta(5) appears to bind RGS proteins in vivo, its association with Ggamma proteins in vivo has not been clearly demonstrated. It is unclear how Gbeta(5) might influence RGS activity. In C. elegans there are exactly two GGL-containing RGS proteins, EGL-10 and EAT-16, and they inhibit Galpha(o) and Galpha(q) signaling, respectively. ⋯ Gbeta(5) functions in vivo complexed with GGL-containing RGS proteins. In the absence of Gbeta(5), these RGS proteins have little or no function. The formation of RGS-Gbeta(5) complexes is required for the expression or stability of both the RGS and Gbeta(5) proteins. Appropriate RGS-Gbeta(5) complexes regulate both Galpha(o) and Galpha(q) proteins in vivo.
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Current biology : CB · Mar 1999
Association of the type 1 protein phosphatase PP1 with the A-kinase anchoring protein AKAP220.
The cyclic AMP (cAMP)-dependent protein kinase (PKA) and the type 1 protein phosphatase (PP1) are broad-specificity signaling enzymes with opposing actions that catalyze changes in the phosphorylation state of cellular proteins. Subcellular targeting to the vicinity of preferred substrates is a means of restricting the specificity of each enzyme [1] [2]. Compartmentalization of the PKA holoenzyme is mediated through association of the regulatory subunits with A-kinase anchoring proteins (AKAPs), whereas a diverse family of phosphatase-targeting subunits directs the location of the PP1 catalytic subunit (PP1c) [3] [4]. ⋯ Immunoprecipitation of PP1 from cell extracts resulted in a 10.4 +/- 3.8-fold enrichment of PKA activity. AKAP220 co-purified with PP1c by affinity chromatography on microcystin sepharos Immunocytochemical analysis demonstrated that the kinase, the phosphatase and the anchoring protein had distinct but overlapping staining patterns in rat hippocampal neurons. Collectively, these results provide the first evidence that AKAP220 is a multivalent anchoring protein that maintains a signaling scaffold of PP1 and the PKA holoenzyme.