Force redistribution in clathrin-mediated endocytosis revealed by coiled-coil force sensors.

Forces are central to countless cellular processes, yet in vivo force measurement at the molecular scale remains difficult if not impossible. During clathrin-mediated endocytosis, forces produced by the actin cytoskeleton are transmitted to the plasma membrane by a multiprotein coat for membrane deformation. However, the magnitudes of these forces remain unknown. Here, we present new in vivo force sensors that induce protein condensation under force. We measured the forces on the fission yeast Huntingtin-Interacting Protein 1 Related (HIP1R) homolog End4p, a protein that links the membrane to the actin cytoskeleton. End4p is under ~19-piconewton force near the actin cytoskeleton, ~11 piconewtons near the clathrin lattice, and ~9 piconewtons near the plasma membrane. Our results demonstrate that forces are collected and redistributed across the endocytic machinery.