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

• Published in: PloS one 2024-05, Vol.19 (5), p.e0295701-e0295701
• Main Authors: Mahadik, Snehal S, Burt, Emily K, Lundquist, Erik A
• Format: Article
• Language: English
• Subjects: Actin; Animals; Animals, Genetically Modified; Axon guidance; Bacterial infections; Biology and Life Sciences; Caenorhabditis elegans; Caenorhabditis elegans - genetics; Caenorhabditis elegans - growth & development; Caenorhabditis elegans - metabolism; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Care and treatment; Cell adhesion & migration; Cell migration; Cell Movement; Cell Polarity; Cones; Dimerization; Genetic aspects; Genetic engineering; Genome editing; Genomes; Genomics; Growth; Growth cones; Growth Cones - metabolism; Health aspects; Kinases; Morphology; Mutants; Mutation; Netrin Receptors - genetics; Netrin Receptors - metabolism; Netrins; Patient outcomes; Phenotypes; Polarity; Receptors; Receptors, Cell Surface; Research and Analysis Methods; Steroid receptor coactivator 1; Tyrosine; Vesicle fusion
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0295701

The Polarity/Protusion model of UNC-6/Netrin function in axon repulsion does not rely on a gradient of UNC-6/Netrin. Instead, the UNC-5 receptor polarizes the VD growth cone such that filopodial protrusions are biased to the dorsal leading edge. UNC-5 then inhibits growth cone protrusion ventrally based upon this polarity, resulting in dorsally-biased protrusion and dorsal migration away from UNC-6/Netrin. While previous studies have shown that UNC-5 inhibits growth cone protrusion by destabilizing actin, preventing microtubule + end entry, and preventing vesicle fusion, the signaling pathways involved are unclear. 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 of src-1 was generated, and mutants displayed unpolarized growth cones with increased size, similar to unc-5 mutants. Transgenic expression of src-1(+) in VD/DD neurons resulted in smaller growth cones, and rescued growth cone polarity defects of src-1 mutants, indicating cell-autonomous function. Transgenic expression of a putative kinase-dead src-1(D831A) mutant caused a phenotype similar to src-1 loss-of-function, suggesting that this is a dominant negative mutation. The D381A mutation was introduced into the endogenous src-1 gene by genome editing, which also had a dominant-negative effect. Genetic interactions of src-1 and unc-5 suggest 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-1 function was not required for the effects of activated myr::unc-5, suggesting that SRC-1 might be involved in UNC-5 dimerization and activation by UNC-6, of which myr::unc-5 is independent. In sum, these results show that SRC-1 acts with UNC-5 in growth cone polarity and inhibition of protrusion.