Figure 2. Four mechanisms proposed to account for CME shutdown during mitosis.

(A) Mitotic phosphorylation. Important molecules in the basic layer or second layer of CME proteins are phosphorylated by mitotic kinases. This phosphorylation renders them unable to interact with their partners, thus stalling CME. (B) Altered membrane tension. During endocytosis, the CME machinery (green arrow) must overcome three forces: the tension in the bilayer plane (T_m), interactions between the membrane and cytoskeleton (γ) and the stiffness of bending a membrane (B). B depends on the radius of the invaginated membrane. The CME machinery can overcome the sum of these forces easily during interphase, but cannot do so during mitosis. (C) Mitotic moonlighting. This is a variation on the first mechanism where a key protein is involved in another function during mitosis and its unavailability for CME stalls the pathway. It may or may not involve mitotic phosphorylation. (D) Mitotic spindle-dependent inhibition. The reorganization of the microtubule network and associated motors during mitosis could inhibit late stages of CME.