The functional analysis of NPXY motif in β integrin in vivo.
NPXY (Asn-Pro-X-Tyr) is a conserved tyrosine phosphorylation motif that binds to PTB (phospho-tyrosine binding) domain of other protein. Integrins, a heterodimeric cell surface receptor for extracellular matrix (ECM), include two NPXY motifs in tandem on the cytoplasmic tails of β subunits. I generated a tyrosine to glutamate mutation mimicking constitutive phosphorylation of NPXY in βpat-3 integrin of Caenorhabditis elegans. The transgenic animals displayed disorganized muscle actin and abnormal gonad migration and tail morphology, suggesting that the phosphorylation of tyrosine causes defective phenotypes. In addition, the transgenic animals produced the high number of males, implying that the transgenic animals are similar to him-4/hemicentin alleles and that the lack of him-4 may cause the phosphorylation of NPXY. Genetic analyses revealed that tyrosine to phenylalanine mutations in both positions, βpat-3(YYFF), was able to suppress high incidence in male, mating ability, and egg-laying phenotypes of him-4 mutant, suggesting that a function of him-4 is to prevent the phosphorylation of βpat-3 NPXY. Taken together, our data suggest that changes in the ECM regulate the phosphorylation of the integrin NPXY.