PCMD-1 stabilizes the PCM scaffold and facilitates centriole separation

Centrosomes are highly dynamic organelles, and maintaining their stability is crucial for spindle pole integrity and bipolar spindle formation. Centrosomes consist of a pair of centrioles surrounded by the PCM. In Caenorhabditis elegans, interactions between the scaffold protein SPD-5 and kinase PLK-1 are essential for PCM formation. However, how PCM stability is established and maintained remains unclear. We address this by analyzing the function of PCMD-1, a protein mainly localizing to centrioles. We show that CDK-1 primes PCMD-1 for PLK-1 phosphorylation. Mutations in PLK-1 docking sites abolish PCMD-1 phosphorylation and SPD-5 binding in vitro and destabilize the PCM scaffold in vivo. As a result, microtubule-pulling forces cannot be relayed to centrioles, delaying their separation. Our findings reveal that PCMD-1 is critical for PCM stability and timely centriole separation during PCM disassembly. We propose that PCMD-1 initiates scaffold assembly by biasing the PCM core toward intrinsic order, acting as a seed that propagates throughout the scaffold to ensure structural integrity.