Binding of a number of hormones and steroids, including testosterone, progesterone, and cholesterol, has been found to occur with sigma-2 receptors, though in some cases with lower affinity than to the sigma-1 receptor. Signaling caused by this binding is thought to occur via a calcium secondary messenger and calcium-dependent phosphorylation, and in association with sphingolipids following endoplasmic reticulum release of calcium. Known effects include decrease of expression of effectors in the mTOR pathway, and suppression of cyclin D1 and PARP-1.