Selective disruption of microtubule formation at the nuclear envelope impairs the bone resorption capacity of osteoclasts

Microtubule organization plays a central role in cell differentiation, orchestrating essential processes such as cell polarization, mechanotransduction, organelle positioning, and intracellular transport. A hallmark of many differentiated cells is the transition from a centrosomal to a non-centrosomal microtubule-organizing center (MTOC). Here, we demonstrate that both centrosomal and nuclear envelope (NE)-associated MTOCs coexist in osteoclasts. We show that the key players for NE-MTOC formation, AKAP6β and nesprin-1α, previously considered muscle-specific, are upregulated during osteoclast differentiation, suggesting a conserved role in NE-MTOC assembly across cell types. Targeted depletion of AKAP6 in RAW264.7-derived osteoclasts led to the displacement of the Golgi and MTOC-associated proteins PCM1, pericentrin, and CDK5RAP2 from the NE, while their centrosomal localization remained intact. This selectively impaired microtubule nucleation from the NE without disrupting centrosomal microtubule activity, enabling a functional dissection of the two MTOCs. Loss of NE-MTOC activity, by AKAP6 depletion, impaired podosome formation and significantly reduced bone resorption capacity, highlighting the distinct and essential role of NE-derived microtubules in osteoclast function.

AKAP6β; Bone resorption; Microtubule-organizing center; Nesprin-1α; Osteoclast; Podosome.