Centrosome-derived microtubule radial array, PCM-1 protein, and primary cilia formation.

In animal cells, the centrosome nucleates and anchors microtubules (MT), forming their radial array. During interphase centrosome-derived MT, aster can either team up with other MT network or function in an autonomous manner. What is the function of the centrosome-derived MT aster? We suggested that it might play an important role in the formation of the primary cilium, the organelle obligatorily associated with the centrosome. PCM-1 (PeriCentriolar Matrix 1) protein, which participates in the organization of the primary cilium, is a part of pericentiolar satellites. They are transported to the centrosome along MTs by the motor protein dynein in a complex with its cofactor dynactin. Previously, we showed that SLK/LOSK phosphorylated the p150 subunit of dynactin, thus promoting its centrosomal targeting followed by its participation in the retention of microtubules. Here, we found that under the repression of SLK/LOSK activity, the PCM-1 protein lost its pericentrosomal localization and was being dispersed throughout the cytoplasm. Despite that the alanine and glutamine mutants of p150 had opposite effects on PCM-1 localization, they associated with PCM-1 to the same extent. The occurrence of primary cilia also significantly decreased when SLK/LOSK was repressed. These defects also correlated with a disturbance of the long-range transport in cells, whereas dynein-depending motility was intact. Treatment with the GSK-3β kinase inhibitor also resulted in the loss of the centrosome-derived MT aster, dispersion of PCM-1 over the cytoplasm, and reduction of primary cilia occurrence. Thus, kinases involved in the centrosome-derived MT aster regulation can indirectly control the formation of primary cilia in cells.