Modulation of Rho guanine exchange factor Lfc activity by protein kinase A-mediated phosphorylation.
Lfc is a guanine nucleotide exchange factor (GEF) for Rho that demonstrates an unusual ability to associate with microtubules. While several phosphorylated residues have been detected in the Lfc polypeptide, the mechanism(s) by which phosphorylation regulates the exchange activity of Lfc remains unclear. We confirm that Lfc is a phosphorylated protein and demonstrate that 14-3-3 interacts directly and in a phosphorylation-dependent manner with Lfc. We identify AKAP121 as an Lfc-binding protein and show that Lfc is phosphorylated in an AKAP-dependent manner by protein kinase A (PKA). Forskolin treatment induced 14-3-3 binding to Lfc and suppressed the exchange activity of wild-type Lfc on RhoA. Importantly, a mutant of Lfc that is unable to associate with 14-3-3 proteins was resistant to inhibition by forskolin. Tctex-1, a dynein motor light chain, binds to Lfc in a competitive manner with 14-3-3.
Meiri
David
D
Ontario Cancer Institute, Toronto Medical Discovery Tower, MaRS East Tower, 101 College St., Toronto, Ontario M5G 1L7, Canada.
Greeve
Melissa A
MA
Brunet
Andrea
A
Finan
Dina
D
Wells
Clark D
CD
LaRose
Jose
J
Rottapel
Robert
R
D048948:14-3-3 Proteins / Q000378:metabolism; D054758:A Kinase Anchor Proteins / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D016384:Consensus Sequence; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004398:Dyneins; D004789:Enzyme Activation; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D051381:Rats; D064067:Rho Guanine Nucleotide Exchange Factors; D022502:Stress Fibers / Q000201:enzymology; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D056427:t-Complex Genome Region
D048948:14-3-3 Proteins; D054758:A Kinase Anchor Proteins; C105137:AKAP1 protein, human; C577356:ARHGEF2 protein, human; C533388:Dynlt1 protein, rat; C533386:Dynlt1b protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D064067:Rho Guanine Nucleotide Exchange Factors; D017868:Cyclic AMP-Dependent Protein Kinases; D004398:Dyneins; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020742:rhoA GTP-Binding Protein