The membrane anchor R7BP controls the proteolytic stability of the striatal specific RGS protein, RGS9-2.
A member of the RGS (regulators of G protein signaling) family, RGS9-2 is a critical regulator of G protein signaling pathways that control locomotion and reward signaling in the brain. RGS9-2 is specifically expressed in striatal neurons where it forms complexes with its newly discovered partner, R7BP (R7 family binding protein). Interaction with R7BP is important for the subcellular targeting of RGS9-2, which in native neurons is found in plasma membrane and its specializations, postsynaptic densities. Here we report that R7BP plays an additional important role in determining proteolytic stability of RGS9-2. We have found that co-expression with R7BP dramatically elevates the levels of RGS9-2 and its constitutive subunit, Gbeta5. Measurement of the RGS9-2 degradation kinetics in cells indicates that R7BP markedly reduces the rate of RGS9-2.Gbeta5 proteolysis. Lentivirus-mediated RNA interference knockdown of the R7BP expression in native striatal neurons results in the corresponding decrease in RGS9-2 protein levels. Analysis of the molecular determinants that mediate R7BP/RGS9-2 binding to result in proteolytic protection have identified that the binding site for R7BP in RGS proteins is formed by pairing of the DEP (Disheveled, EGL-10, Pleckstrin) domain with the R7H (R7 homology), a domain of previously unknown function that interacts with four putative alpha-helices of the R7BP core. These findings provide a mechanism for the regulation of the RGS9 protein stability in the striatal neurons.
Anderson
Garret R
GR
Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455.
Semenov
Arthur
A
Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455.
Song
Joseph H
JH
Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455.
Martemyanov
Kirill A
KA
Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455. Electronic address: martemyanov@umn.edu.
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000166:cytology / Q000502:physiology; D002460:Cell Line; D000072261:Dishevelled Proteins; D019204:GTP-Binding Proteins; D015870:Gene Expression; D006801:Humans; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D000072261:Dishevelled Proteins; D010750:Phosphoproteins; C499440:R7BP protein, mouse; D020710:RGS Proteins; C116925:regulator of g-protein signaling 9; D019204:GTP-Binding Proteins