G alpha12 is targeted to the mitochondria and affects mitochondrial morphology and motility.
G alpha12 constitutes, along with G alpha13, one of the four families of alpha subunits of heterotrimeric G proteins. We found that the N terminus of G alpha12, but not those of other G alpha subunits, contains a predicted mitochondrial targeting sequence. Using confocal microscopy and cell fractionation, we demonstrated that up to 40% of endogenous G alpha12 in human umbilical vein endothelial cells colocalize with mitochondrial markers. N-terminal sequence of G alpha12 fused to GFP efficiently targeted the fusion protein to mitochondria. G alpha12 with mutated mitochondrial targeting sequence was still located in mitochondria, suggesting the existence of additional mechanisms for mitochondrial localization. Lysophosphatidic acid, one of the known stimuli transduced by G alpha12/13, inhibited mitochondrial motility, while depletion of endogenous G alpha12 increased mitochondrial motility. G alpha12Q229L variants uncoupled from RhoGEFs (but not fully functional activated G alpha12Q229L) induced transformation of the mitochondrial network into punctate mitochondria and resulted in a loss of mitochondrial membrane potential. All examined G alpha12Q229L variants reduced phosphorylation of Bcl-2 at Ser-70, while only mutants unable to bind RhoGEFs also decreased cellular levels of Bcl-2. These G alpha12 mutants were also more efficient Hsp90 interactors. These findings are the first demonstration of a heterotrimeric G protein alpha subunit specifically targeted to mitochondria and involved in the control of mitochondrial morphology and dynamics.
Andreeva
Alexandra V
AV
Department of Pharmacology, University of Illinois at Chicago, 909 S. Wolcott Ave., Chicago, IL 60612, USA.
Kutuzov
Mikhail A
MA
Voyno-Yasenetskaya
Tatyana A
TA
D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D042783:Endothelial Cells / Q000378:metabolism / Q000648:ultrastructure; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D009068:Movement; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011485:Protein Binding; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors
D020662:Guanine Nucleotide Exchange Factors; D018841:HSP90 Heat-Shock Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D048031:JNK Mitogen-Activated Protein Kinases; D044365:GTP-Binding Protein alpha Subunits, G12-G13