Regulator of G protein signaling RGS3T is localized to the nucleus and induces apoptosis.
RGS3 belongs to a family of the regulators of G protein signaling (RGS). We previously demonstrated that cytosolic RGS3 translocates to the membrane to inhibit G(q/11) signaling (Dulin, N. O., Sorokin, A., Reed, E., Elliott, S., Kehrl, J., and Dunn, M. J. (1999) Mol. Cell. Biol. 19, 714-723). This study examines the properties of a recently identified truncated variant termed RGS3T. Both RGS3 and RGS3T bound to endogenous Galpha(q/11) and inhibited endothelin-1-stimulated calcium mobilization and mitogen-activated protein kinase activity to a similar extent. However, unlike cytosolically localized RGS3, RGS3T was found predominantly in the nucleus and partially in the plasma membrane. Furthermore, RGS3T, but not RGS3, caused cell rounding and membrane blebbing. Finally, 44% of RGS3T-transfected cells underwent apoptosis after serum withdrawal, which was significantly higher than that of RGS3-transfected cells (7%). Peptide sequence analysis revealed two potential nuclear localization signal (NLS) sequences in RGS3T. Further truncation of the RGS3T N terminus containing putative NLSs resulted in a significant reduction of nuclear versus cytoplasmic staining of the protein. Moreover, this truncated RGS3T no longer induced apoptosis. In summary, RGS3 and its truncated variant RGS3T are similar in their ability to inhibit G(q/11) signaling but are different in their intracellular distribution. These data suggest that, in addition to being a GTPase-activating protein, RGS3T has other distinct functions in the nucleus of the cell.
Dulin
N O
NO
Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois 606122-7343, USA. dulin@uic.edu
Pratt
P
P
Tiruppathi
C
C
Niu
J
J
Voyno-Yasenetskaya
T
T
Dunn
M J
MJ
D000818:Animals; D017209:Apoptosis; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D006224:Cricetinae; D019332:Endothelin-1 / Q000494:pharmacology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019204:GTP-Binding Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins; D014644:Genetic Variation; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019913:Nuclear Localization Signals / Q000502:physiology; D020710:RGS Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection
D019332:Endothelin-1; D020690:GTPase-Activating Proteins; D019913:Nuclear Localization Signals; D020710:RGS Proteins; C485898:RGS3 protein, human; D011994:Recombinant Proteins; C415085:Rgs3 protein, mouse; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium