Proximity Labeling Reveals Spatial Regulation of the Anaphase-Promoting Complex/Cyclosome by a Microtubule Adaptor

The anaphase-promoting complex/cyclosome (APC/C) coordinates
advancement
through mitosis via temporally controlled polyubiquitination events.
Despite the long-appreciated spatial organization of key events in
mitosis mediated largely by cytoskeletal networks, the spatial regulation
of APC/C, the major mitotic E3 ligase, is poorly understood. We describe
a microtubule-resident protein, PLEKHA5, as an interactor of APC/C
and spatial regulator of its activity in mitosis. Microtubule-localized
proximity biotinylation tools revealed that PLEKHA5 depletion decreased
APC/C association with the microtubule cytoskeleton, which prevented
efficient loading of APC/C with its coactivator CDC20 and led to reduced
APC/C E3 ligase activity. PLEKHA5 knockdown delayed mitotic progression,
causing accumulation of APC/C substrates dependent upon the PLEKHA5–APC/C
interaction in microtubules. We propose that PLEKHA5 functions as
an adaptor of APC/C that promotes its subcellular localization to
microtubules and facilitates its activation by CDC20, thus ensuring
the timely turnover of key mitotic APC/C substrates and proper progression
through mitosis.