Direct interaction of pericentrin with cytoplasmic dynein light intermediate chain contributes to mitotic spindle organization

Pericentrin is a conserved protein of the cen centrosome involved in microt ubule organization. To better understand pericentrin function, we overexpre ssed the protein in somatic cells and assayed for changes in the compositio n and function of mitotic spindles and spindle poles, Spindles in pericentr in-overexpressing cells were disorganized and mispositioned, and chromosome s were misaligned and missegregated during cell division, giving rise to an euploid cells. We unexpectedly found that levels of the molecular motor cyt oplasmic dynein were dramatically reduced at spindle poles. Cytoplasmic dyn ein was diminished at kinetochores also, and the dynein-mediated organizati on of the Golgi complex was disrupted. Dynein coimmunoprecipitated with ove rexpressed pericentrin, suggesting that the motor was sequestered in the cy toplasm and was prevented from associating with its cellular targets. Immun oprecipitation of endogenous pericentrin also pulled down cytoplasmic dynei n in untransfected cells. To define the basis for this interaction, pericen trin was coexpressed with cytoplasmic dynein heavy (DHCs), intermediate (DI Cs), and light intermediate (LICs) chains, and the dynamitin and p150(Glued ) subunits of dynactin. Only the LICs coimmunoprecipitated with pericentrin . These results provide the first physiological role for LIC, and they sugg est that a pericentrin-dynein interaction in vivo contributes to the assemb ly, organization, and function of centrosomes and mitotic spindles.