SRC-1 controls growth cone polarity and protrusion with the UNC-6/Netrin receptor UNC-5 inCaenorhabditis elegans

Abstract

AbstractIn the Polarity/Protusion model of growth cone migration away from the guidance cue UNC-6/Netrin, the UNC-5 receptor polarizes the VD growth cone such that filopodial protrusions are biased to the dorsal leading edge of the growth cone. UNC-5 also inhibits growth cone protrusion ventrally based upon this polarity. The SRC-1 tyrosine kinase has been previously shown to physically interact with and phosphorylate UNC-5, and to act with UNC-5 in axon guidance and cell migration. Here, the role of SRC-1 in VD growth cone polarity and protrusion is investigated. A precise deletion ofsrc-1was generated, and mutants displayed unpolarized growth cones with increased size, similar tounc-5mutants. Transgenic expression ofsrc-1(+)in VD/DD neurons resulted in smaller growth cones, and rescued growth cone polarity defects ofsrc-1mutants, indicating cell-autonomous function. Transgenic expression of a putative kinase-deadsrc-1(D831A)mutant caused a phenotype similar tosrc-1loss-of-function, suggesting that this is a dominant negative mutation. The D381A mutation was introduced into the endogenoussrc-1gene by genome editing, which also had a dominant-negative effect. Genetic interactions ofsrc-1andunc-5suggest they act in the same pathway on growth cone polarity and protrusion, but might have overlapping, parallel functions in other aspects of axon guidance.src-1function was not required for the effects of activatedmyr::unc-5, suggesting that SRC-1 might be involved in UNC-5 dimerization and activation by UNC-6, of whichmyr::unc-5is independent. In sum, these results show that SRC-1 acts with UNC-5 in growth cone polarity and inhibition of protrusion.