Basigin (CD147) and calpain 4 (CapnS1) are partners in the generation of traction force but not in mechanosensing.

Traction force and mechanosensing (the ability to sense the mechanical attributes of the environment) are two key factors that enable a cell to modify its behavior during migration. Previously, it was determined that the calpain small subunit, Calpain 4 (CapnS1), regulates traction force production independent of its proteolytic holoenzyme. A proteolytic enzyme is formed by Calpain 4 binding to either of its catalytic partners, Calpain 1 and 2. To further understand how Calpain 4 regulates traction force, we used two-hybrid analysis to identify more components of the traction pathway. We discovered that Basigin, an integral membrane protein and a documented inducer of matrix metalloproteases (MMPs), interacts with Calpain 4 in two-hybrid and pull-down assays. Traction force was reduced when basigin was silenced in MEF cells, and this reduction was also reflected in a similar defect in adhesion formation and in substrate adhesion strength. Unlike Capn4-/- MEF cells, Basigin-deficient cells exhibited normal mechanosensing. Together, these results implicate Basigin in the pathway in which Calpain 4 regulates traction force independent of the catalytic large subunits.