IMMUNOLOCALIZATION OF THE HETEROTRIMERIC KINESIN-RELATED PROTEIN KRP((85 95)) IN THE MITOTIC APPARATUS OF SEA-URCHIN EMBRYOS/

We have used monoclonal antibodies to perform confocal light microscop ic immunolocalization of KRP((85/95)), a heterotrimeric plus-end-direc ted microtubule motor protein, in dividing cells of sea urchin embryos , Embryos were stained during the first division cycle, and dissociate d blastomeres were stained at the 32- to 64-cell stages. Double labeli ng of the dividing cells with anti-tubulin and anti-KRP((85/95) showed a clear concentration of the motor protein in the mitotic apparatus; KRP((85/95)) appeared to associate with pericentriolar regions during prophase, with kinetochore-to-pole microtubules during metaphase, and, in a striking fashion, with the spindle interzone during anaphase. KR P((85/95)) began to accumulate in the interzone immediately following chromosome separation and the area of concentration expanded with the lengthening of the interzonal region during anaphase, During telophase KRP((85/95)), appeared to disperse with the establishment of the clea vage furrow and did not concentrate in the midbody. KRP((85/95))) Stai ning in the mitotic apparatus was punctate and detergent-sensitive, su ggesting an association with membranous vesicles, but unlike kinesin, KRP((85/95)) did not appear to codistribute with calsequestrin-contain ing endoplasmic reticulum. Finally, KRP((85/95)) appears to be present in dividing blastomeres up to at least the blastula stage, but, unlik e kinesin, it is not expressed in terminally differentiated, nonmitoti c coelomocytes of the adult animal. These results suggest that the exp ression and targeting of KRP((85/95)), and kinesin differ and that KRP ((85/95)) may play a role in vesicle transport during embryonic cell d ivision. (C) 1995 Academic Press, Inc.