Scientists have discovered how blood cells release an important signaling fat called sphingosine-1-phosphate, or S1P, into the bloodstream.

S1P plays an important role in keeping blood vessels healthy, helping immune cells move around the body, and supporting normal cell function. To carry out these roles, S1P must first leave the cells in which it is produced. However, it cannot pass through the cell membrane freely and on its own. Instead, it relies on specialised proteins that act like gateways. One such gateway is MFSD2B, a protein found mainly in red blood cells and platelets.

In the new study, published in Nature Communications, researchers used cryo-electron microscopy (cryo-EM), computer simulations, and protein engineering to capture a detailed view of MFSD2B while S1P was sitting inside it.