MARK2
MARK2, also known as Par-1, is a microtubule affinity-regulating kinase central to cell polarity. Activated by LKB1, MARK2 phosphorylates microtubule-associated proteins to modulate the cytoskeleton and phosphorylates the polarity protein Par-3, a reaction required for tight junction assembly in epithelial cells. In neurons it governs axon-dendrite specification, and conserved orthologs control anterior-posterior patterning in Caenorhabditis elegans embryos. MARK2-null mice show growth retardation, male and female infertility, immune dysfunction, and behavioral abnormalities, revealing broad organismal functions. Because Par-1 was first defined in yeast genetic screens, MARK2 stands as the canonical example of a polarity kinase conserved from worms to mammals.
