Drebrin-like protein regulates body bending of C. elegans via suppression of NCA cation leak channels

Drebrin-like protein (DBN-1) in C. elegans is an adaptor protein that connects different cellular pathways to the actin cytoskeleton. Using a CRISPR-Cas9 system, we generated a new dbn-1 allele, which lacks 80% of C-terminal part of DBN-1. The mutant displays a striking hyper-bending locomotion phenotype and body posture with two times stronger curvature than wild type. We show by atomic force microscopy that the muscle tone of the mutant remains unaffected. Aiming to track down the cause of hyper-bending, we performed genetic epistasis experiments. We found that mutations in the Rho-specific guanine-nucleotide exchange factor (GEF) domain of UNC-73 (Trio), pan-neuronal expression of dominant negative RHO-1 and mutations in NCA (NALCN) cation leak channels all suppressed hyper-bending in the dbn-1 mutant. These data indicate that DBN-1 negatively regulates the activity of both NCA-1 and NCA-2 channels, opposing RHO-1 in the non-canonical Gq pathway. We conclude that DBN-1 is an important component of the neuronal signalling cascade that controls the degree of C. elegans body bending during locomotion.