Association of 14-3-3 Proteins with Centrosomes

ABSTRACT: The 14-3-3 proteins are involved in diverse signal transduction pathways and interact physically with a wide variety of proteins. Here, we report the partial sequence analysis of a human spleen 14-3-3 protein, which was identified as a variant form of the ε isoform. A peptide antibody generated to the variant 14-3-3 localizes in the centrosome and spindle apparatus of mouse leukemic FDCP cells by immunofluorescence microscopy. Immunoblots of centrosomes isolated by sucrose density gradient centrifugation of cell lysates disclose only the ε and γ isoforms, while total cellular lysates contain the ε, γ, β and ζ isoforms of 14-3-3. These data suggest that a subset of total cellular 14-3-3 proteins are localized in the centrosomes and spindle apparatus. A differential localization of the centrosomal 14-3-3 was observed in mouse 3T3 cells. Serum-starved (quiescent) cells lack the centrosomal 14-3-3, but upon serum-stimulation of these quiescent cells, the centrosomal 14-3-3 reappears. We propose that a subset of intracellular 14-3-3 proteins are localized in the centrosome and spindle apparatus, and may in fact, link mitogenic signaling, the cell cycle, and perhaps the centrosome duplication cycle as well.