Splice variants of SmgGDS control small GTPase prenylation and membrane localization. J Biol Chem 2010 Nov 12;285(46):35255-66
Date
08/17/2010Pubmed ID
20709748Pubmed Central ID
PMC2975149DOI
10.1074/jbc.M110.129916Scopus ID
2-s2.0-78149231569 (requires institutional sign-in at Scopus site) 65 CitationsAbstract
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 CLAuthor
Carol L. Williams PhD Professor in the Pharmacology and Toxicology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Alternative SplicingAmino 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