TBC1D4

Insulin is one of the things that does that.

Insulin binds its receptor, and the signal runs through a few different steps until it gets to a kinase called AKT, and AKT phosphorylates a protein called TBC1D4.

TBC1D4 is a break.

If you phosphorylate it, the break comes off, the vesicles move, GLUT4 is installed in the cell membrane, and sugar comes in.

Muscle contraction does the same job, but by a different route.

As ATP is used for contraction, the ratio of AMP to ATP goes up, because you're getting rid of some ATP.

And that all activates AMP kinase, which is the cell's energy sensor.

AMP kinase, like kinases do, phosphorylates TBC1D1, the sister protein to TBC1D4, and it releases a different break on the same vesicles storing GLUT4, which again end up on the surface of the cell and sugar can come in.