MEC4

MEC-4 is a gene in the nematode Caenorhabditis elegans that encodes a subunit of a mechanosensory ion channel. It belongs to the degenerin/epithelial sodium channel (DEG/ENaC) family and is expressed in the six touch receptor neurons. The MEC-4 protein is a membrane protein with two transmembrane domains and a sizeable extracellular loop, and it forms part of a heteromeric channel that is activated by mechanical stimulation of the worm's cuticle.

In the nervous system, MEC-4 forms a core channel with other subunits such as MEC-10, and is modulated by accessory proteins MEC-2 and MEC-6, which influence channel localization and function. The channel conducts cations, largely sodium, and its activity is essential for normal gentle touch sensation in C. elegans.

Genetic mutations in mec-4 alter touch sensitivity: loss-of-function alleles reduce or abolish gentle touch responses, while certain gain-of-function mutations cause neurodegeneration of the touch neurons due to constitutive channel activity and ionic imbalance.

MEC-4 has been central to studies of mechanotransduction and neurodegeneration. As a member of the DEG/ENaC family, it provided insight into how mechanical forces gate ion channels and how channel dysregulation can lead to neuron death. The MEC-4/MEC-10 channel complex remains a model for studying the molecular basis of touch sensation across species.