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Splice variants of SmgGDS control small GTPase prenylation and membrane localization. J Biol Chem 2010 Nov 12;285(46):35255-66

Date

08/17/2010

Pubmed ID

20709748

Pubmed Central ID

PMC2975149

DOI

10.1074/jbc.M110.129916

Scopus ID

2-s2.0-78149231569 (requires institutional sign-in at Scopus site)   65 Citations

Abstract

Ras and Rho small GTPases possessing a C-terminal polybasic region (PBR) are vital signaling proteins whose misregulation can lead to cancer. Signaling by these proteins depends on their ability to bind guanine nucleotides and their prenylation with a geranylgeranyl or farnesyl isoprenoid moiety and subsequent trafficking to cellular membranes. There is little previous evidence that cellular signals can restrain nonprenylated GTPases from entering the prenylation pathway, leading to the general belief that PBR-possessing GTPases are prenylated as soon as they are synthesized. Here, we present evidence that challenges this belief. We demonstrate that insertion of the dominant negative mutation to inhibit GDP/GTP exchange diminishes prenylation of Rap1A and RhoA, enhances prenylation of Rac1, and does not detectably alter prenylation of K-Ras. Our results indicate that the entrance and passage of these small GTPases through the prenylation pathway is regulated by two splice variants of SmgGDS, a protein that has been reported to promote GDP/GTP exchange by PBR-possessing GTPases and to be up-regulated in several forms of cancer. We show that the previously characterized 558-residue SmgGDS splice variant (SmgGDS-558) selectively associates with prenylated small GTPases and facilitates trafficking of Rap1A to the plasma membrane, whereas the less well characterized 607-residue SmgGDS splice variant (SmgGDS-607) associates with nonprenylated GTPases and regulates the entry of Rap1A, RhoA, and Rac1 into the prenylation pathway. These results indicate that guanine nucleotide exchange and interactions with SmgGDS splice variants can regulate the entrance and passage of PBR-possessing small GTPases through the prenylation pathway.

Author List

Berg TJ, Gastonguay AJ, Lorimer EL, Kuhnmuench JR, Li R, Fields AP, Williams CL

Author

Carol L. Williams PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Alternative Splicing
Amino Acid Sequence
Blotting, Western
Cell Line, Tumor
Cell Membrane
Gene Expression
Green Fluorescent Proteins
Guanine Nucleotide Exchange Factors
Guanosine Diphosphate
Guanosine Triphosphate
HEK293 Cells
Humans
Immunoprecipitation
Lung
Lung Neoplasms
Microscopy, Fluorescence
Molecular Sequence Data
Monomeric GTP-Binding Proteins
Mutation
Protein Binding
Protein Isoforms
Protein Prenylation
RNA Interference
Reverse Transcriptase Polymerase Chain Reaction
rap1 GTP-Binding Proteins