The pericentriolar lattice of PtK₂ cells exhibits temperature and calcium-modulated behavior

In this study, we demonstrate that manipulations of temperature and free calcium alter the morphology of the centrin-containing pericentriolar lattice of PtK₂ cells. Immunofluorescence microscopy reveals that low-temperature incubation (4°C) causes anti-centrin-labeled pericentrosomal spots to coalesce in the peripheral cytoplasm, and fuses small spots into larger spots near the cell center. At electron microscopic resolution, well-formed pericentriolar satellites appear around the centrioles in response to incubation at 4°C. Elevated free calcium enhances these low-temperature-dependent effects. The data suggest that pericentrosomal spots correspond to one or more pericentriolar satellites, and that pericentriolar satellites and centrosomal matrix are interconvertable forms of the same material. Transient elevation of intracellular free calcium at 37°C from a basal level of 3.7x10^-8 M to a peak level of 2.0x10^-7 M within 30 seconds with ionomycin results in a 35% increase in pericentrosomal spot number throughout the cytoplasm. The number of pericentrosomal spots is 50% larger 2 minutes after ionomycin addition; these spots are also nearer to the cell center as compared to 30 seconds after ionomycin addition. As intracellular free calcium returns to a basal level over 5 minutes, the number of spots and their cellular distribution resume a pretreatment value and pattern. We interpret these observations to indicate movement of pericentrosomal spots towards the cell center in response to the flux in intracellular free calcium. Alternatively, it is possible that no movement has occurred, but that the rise in free calcium has unmasked an epitope responsive to our anti-centrin antiserum. Regardless of the interpretation, we conclude that the pericentriolar lattice exhibits calcium-modulated behavior.