Extracellular proteins organize the mechanosensory channel complex in C. elegans touch receptor neurons.

Specialized extracellular matrix (ECM) is associated with virtually every mechanosensory system studied. C. elegans touch receptor neurons have specialized ECM and attach to the surrounding epidermis. The mec-1 gene encodes an ECM protein with multiple EGF and Kunitz domains. MEC-1 is needed for the accumulation of the collagen MEC-5 and other ECM components, attachment, and, separately, for touch sensitivity. MEC-1 and MEC-5 bind to touch processes uniformly and in puncta. These puncta colocalize with and localize the mechanosensory channel complex in the touch neurons. In turn, the production of the MEC-1 and MEC-5 puncta appears to rely on interactions with the neighboring epidermal tissue. These and other observations lead us to propose that extracellular, but not cytoskeletal, tethering of the degenerin channel is needed for mechanosensory transduction. Additionally, our experiments demonstrate an important role of the ECM in organizing the placement of the channel complex.