The NPxY motifs in the β integrin regulate serotonin response and mechanosensation in C. elegans

BackgroundIntegrin is an {beta} heterodimeric receptor to the extracellular matrix; its binding to the matrix recruits focal adhesions to two NPxY motifs, the tyrosine phosphorylation sites in the cytoplasmic domain. Studies found that replacing tyrosines (Y) with phenylalanines (F) in the motif of {beta}1 integrin displayed little developmental or behavioral defects. However, the tyrosine-to-alanine (A) caused embryonic lethality. ResultsHere we report novel functions of the NPxY motifs in C. elegans pat-3 {beta} integrin. The membrane-proximal non-phosphorylation pat-3(Y792F) mutation caused hypersensitive egg laying in serotonin, which is more prominent than the membrane-distal NPxY804. The double non-phosphorylatable pat-3(YYFF) mutant exhibited serotonin hypersensitivity and defective egg retention. The phosphomimetic NPxY, pat-3(Y804E), mutant displayed a reduced egg laying in response to serotonin and fluoxetine, suggesting that the NPxY phosphorylation is associated with vulval contraction and serotonin sensitivity. Additionally, pat-3(Y792A), pat-3(Y792F), pat-3(Y804E), and pat-3(YYFF) mutants exhibited mechanosensation defects, demonstrating that NPxY phosphorylation regulates sensory neuron activity. Further revealed that exogenous serotonin reduced mechanosensation, while blocking serotonin secretion rescued the mechanosensation of pat-3 NPxY mutants, suggesting that integrin NPxY modulates serotonin levels in C. elegans. ConclusionOur results underscore the functional importance of pat-3 NPxY motifs in muscle and neurons, potentially linking integrin NPxY motifs to neurotransmitter response and mechanosensory functions.