Channels rush in

Channels lurking in vesicles just beneath the cell surface can leap into action by inserting into the plasma membrane, say Vassilios Bezzerides, David Clapham (Harvard Medical School, Boston, MA), and colleagues. The resulting increase in Ca²⁺ current slows down and perhaps changes the outgrowth direction of advancing neurites.

The Boston group saw TRPC5 Ca²⁺ channels transferring into the plasma membrane, as measured by total internal reflection microscopy, electrophysiology, and surface biotinylation, in response to several growth factors. “Instead of controlling just gating, you are controlling availability,” says Clapham.

Recruitment and activation of TRPC5 Ca²⁺ currents were dependent on activated Rac and production of PIP₂. In combination with previous work, this suggests the following scenario: activated growth factor receptors turn on PI3K-mediated production of PIP₃; PIP₃ recruits an exchange...