Mechanosensing refers to a process whereby mechanical inputs are sensed and transduced as a chemical or electrical signal to initiate or accelerate a downstream pathway. Many important biological events are mediated by this process including tissue differentiation, morphogenesis and also in pathophysiological conditions such as tumor progression, but their mechanisms at a molecular level remain poorly understood.
Mechanotransduction signaling in vivo can be triggered by body-wall muscle contractions (elongating C. elegans embryos), cell shape changes (Drosophila embryos), hydrodynamic forces (ventricle of mouse brain), or blood flow (heart development in zebrafish). During C. elegans development, embryos elongate 4-fold without additional cell division or migration. This process is highly robust and invariable. Previous studies demonstrated that hemidesmosomes (cell attachments to the extracellular matrix) play a critical role in mechanosensing by stabilizing the scaffolding protein GIT-1 in response to muscle input, but little is known about how it works at the molecular level (Nature, 2011 (471) 99-103). Therefore we aimed to characterize a putative binding partner of the earliest known effector (GIT-1) of mechanosensing. For this, we used both in vitro and in vivo (CRISPR-CAS9) tools to identify its binding partners (if any). Interestingly, we found that a core component of the hemidesmosome i.e., VAB-10 strongly interacts with GIT-1 molecularly and genetically. Far-Western blotting suggests that purified VAB-10 and GIT-1 interact molecularly in vitro. Genetic interaction studies revealed that a mutation affecting the SH3 domain present within a spectrin repeat of VAB-10 strongly interacts with mutations in git-1, pix-1 and also with pak-1 (players of the mechanotransduction pathway). In double mutants background, embryos arrested prior to the two-fold stage, a phenotype also noticed in hemidesmosome-deficient embryos. This result suggests that the SH3 domain of VAB-10 provides an interaction platform for diverse players in response to physical cues in mechanosensing pathway. We would also like to extend our studies in the context of characterizing mechanosensing properties and molecular cause of such phenotypes using a combination of biophysical tools (AFM) in vitro, and genetic tools (transgenic line) in vivo respectively. Thus, understanding how mechanosensors and their signaling cascades operate should elucidate a cellular phenomenon in a better way.