The function and dynamics of the apical scaffolding protein E3KARP are regulated by cell-cycle phosphorylation.

We examine the dynamics and function of the apical scaffolding protein which consists of two PDZ domains and a tail containing an ezrin-binding domain. The exchange rate of is greatly enhanced during mitosis due to phosphorylation at Ser-303 in its tail region. Whereas E3Kduanyu37 can substitute for the function of the closely related scaffolding protein EBP50/NHERF1 in the formation of interphase microvilli, E3Kduanyu37 S303D cannot. Moreover, the S303D mutation enhances the in vivo dynamics of the E3Kduanyu37 tail alone, whereas in vitro the interaction of E3Kduanyu37 with active ezrin is unaffected by S303D, implicating another factor regulating dynamics in vivo. A-Raf is found to be required for S303 phosphorylation in mitotic cells. Regulation of the dynamics of EBP50 is known to be dependent on its tail region but modulated by PDZ domain occupancy, which is not the case for Of interest, in both cases, the mechanisms regulating dynamics involve the tails, which are the most diverged region of the paralogues and probably evolved independently after a gene duplication event that occurred early in vertebrate evolution.

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