Endocytosis of sex steroids: The hypothesis of free hormones revisited

Receptor-mediated endocytosis is the main mechanism that enables selective transport of macromolecules across the plasma membrane into cells. It is initiated by binding of ligands to endocytic receptors on the cell surface, followed by internalization through clathrin-coated vesicles. Most ligands are delivered to lysosomal compartments for further catabolism, while the unliganded receptors are recycled back to the plasma membrane. The major class of endocytic receptors in mammalian cells is...