| Summary: | Deregulation of the cell cycle is a hallmark of neoplastic transformation and plays a central role in both the initiation and progression of cancer. Members of the NimA-related kinase (NEK) family of protein kinases are emerging as important players in regulation of the eukaryotic cell cycle during normal cell cycle progression and checkpoint activation in response to genotoxic stresses. The focus of this thesis is NEK10, a previously uncharacterized member of the NEK family. While little is known about the biology of NEK10, recent cancer genomics studies have identified NEK10 as a candidate susceptibility gene at chromosome 3p24 in cancer.
Work herein describes a role for NEK10 in the cellular response to ultraviolet (UV) irradiation. NEK10 was required for the activation of ERK1/2 signaling upon UV irradiation, but not in response to mitogens, such as the epidermal growth factor. NEK10 interacted with Raf and MEK and enhanced MEK activity through a novel mechanism involving MEK autoactivation. Significantly, appropriate maintenance of the G2/M checkpoint following UV irradiation required NEK10 expression and ERK1/2 activation. In support of a conserved role for NEK10 in the cellular response to UV irradiation, nekl-4, the NEK10 C.elegans homologue, affected embryonic sensitivity to UV-irradiation.
In search of regulatory inputs into NEK10, using mass spectrometry, our laboratory identified 19 distinct sites of NEK10 phosphorylation. Characterization of a number of these sites revealed a role for intermolecular autophosphorylation in achieving full NEK10 catalytic activity through activation loop phosphorylation on S684 and S688. Further, a C-terminal phosphorylation site on NEK10, S933, was found to be a 14-3-3 binding site, and was essential for NEK10 cytoplasmic to nuclear translocation following UV irradiation.
Taken together, my studies have discovered a role for NEK10 in the engagement of the G2/M cell cycle checkpoint and provided a mechanistic insight into the relationship between NEK10 and the Raf/MEK/ERK cascade, and the control of NEK10 subcellular localization. This work will serve as a foundation for future studies aimed at understanding the molecular mechanism of NEK10 action and its function in development and tumourigenesis.
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