Residues within the first subdomain of the FERM-like domain in focal adhesion kinase are important in its regulation.
We have previously described regulation of focal adhesion kinase (FAK) by its amino-terminal FERM-like domain through an autoinhibitory interaction with its kinase domain (Cooper, L. A., Shen, T. L., and Guan, J. L. (2003) Mol. Cell. Biol. 23, 8030-8041). Here we show that the first two subdomains of the FERM-like domain are independently capable of inhibiting phosphorylation of FAK in trans. We characterized several point mutations within the first subdomain of the FERM-like domain and find that mutation of Lys-38 to alanine results in a FAK mutant that is strongly hyperphosphorylated when expressed in mammalian cells, and promotes increased phosphorylation of the FAK substrate paxillin. A second mutation of Lys-78 to alanine results in a FAK mutant that is underphosphorylated, but can be activated by extracellular matrix stimuli. Like deletion of the amino terminus itself the K38A mutation is phosphorylated in suspension. The Delta375 truncation mutant of FAK is strongly phosphorylated both when Tyr-397 is mutated to phenylalanine, and in the presence of the Src inhibitor, PP2, suggesting that removal of the amino terminus can render FAK Src independent. This is in contrast to the K38A mutant that is not phosphorylated in the Y397F background, and which shows decreased phosphorylation in the presence of the Src inhibitor PP2, suggesting that regulation of FAK by Src is a secondary step in its activation. The K38A mutation weakens the interaction between the amino terminus of FAK and its own kinase domain, and disrupts the ability of the amino terminus to inhibit the phosphorylation of FAK in trans. The K38A mutation of FAK also increases the ability of FAK to promote cell cycle progression and cell migration, suggesting that hyperphosphorylation of this mutant can positively affect FAK function in cells. Together, these data strongly suggest a role for the first FAK subdomain of the FERM domain in its normal regulation and function in the cell.
Cohen
Lee Ann
LA
Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, USA.
Guan
Jun-Lin
JL
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001973:Bromodeoxyuridine / Q000494:pharmacology; D016466:CHO Cells; D002453:Cell Cycle; D002460:Cell Line; D002465:Cell Movement; D006224:Cricetinae; D003598:Cytoskeletal Proteins / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D005109:Extracellular Matrix / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008239:Lysine / Q000737:chemistry; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D051419:Paxillin; D010750:Phosphoproteins / Q000737:chemistry; D010766:Phosphorylation; D017354:Point Mutation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry*; D011743:Pyrimidines / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry; D019061:src-Family Kinases / Q000378:metabolism
C412373:AG 1879; D003598:Cytoskeletal Proteins; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; D011743:Pyrimidines; D014443:Tyrosine; D004247:DNA; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse; D019061:src-Family Kinases; D001973:Bromodeoxyuridine; D008239:Lysine; D000409:Alanine