We have recently been very interested in a non-motor protein, called PRC1, that crosslinks microtubules to form higher-order bundles. We have shown that PRC1 generates viscous resistive forces that increase as microtubule filaments slide faster and increase with a higher concentration of PRC1 crosslinks. We have demonstrated that PRC1 can form clusters under tension that further stabilize the microtubule bundles and clarify how stable anaphase central spindles are built. We have also examined how biochemical regulation by mitotic kinase activity leads to differential bundle mechanics depending on the phosphorylation state of the PRC1 crosslinker. Most recently, we have worked with collaborators in the Meredith Betterton lab at University of Colorado and the Peter Kramer group at RPI to show that a distinct phase transition occurs as sliding microtubules enter a braking phase, resulting from PRC1 clustering and a collapse of the lateral microtubule spacing.
