Autophosphorylation of Tyr397 and its phosphorylation by Src-family kinases are altered in focal-adhesion-kinase neuronal isoforms (original) (raw)

2000, Biochemical Journal

In brain, focal adhesion kinase (FAK) is regulated by neurotransmitters and has a higher molecular mass than in other tissues, due to alternative splicing. Two exons code for additional peptides of six and seven residues (' boxes ' 6 and 7), located on either side of Tyr$*(, which increase its autophosphorylation. Using in situ hybridization and a monoclonal antibody (Mab77) which does not recognize FAK containing box 7, we show that, although mRNAs coding for boxes 6 and 7 have different patterns of expression in brain, FAKj6,7 is the main isoform in forebrain neurons. The various FAK isoforms fused to green fluorescent protein were all targeted to focal adhesions in nonneuronal cells. Phosphorylation-state-specific antibodies were used to study in detail the phosphorylation of Tyr$*(, a critical residue for the activation and function of FAK. The presence of Abbreviations used : FAK, focal adhesion kinase ; SH2, Src-homology 2 ; SH3, Src-homology 3 ; MAP kinase, mitogen-activated protein kinase ; FAT, focal-adhesion targeting ; ERM, ezrin/radixin/moesin ; JAK, Janus kinase ; LPA, lysophosphatidic acid ; GFP, green fluorescent protein ; RPTP, receptorlike protein tyrosine phosphatase ; RT-, reverse transcription.