Cartoon representation of the kinase domain of the phosphatidylinositol 4-kinase 2-alpha. N-lobe is colored in gold, C-lobe in aquamarine, ATP in the active site between the lobes in the stick representation. PDB code: 4PLA.
PI4K2A is composed of a proline-rich N-terminal region and a kinase domain located C-terminally. The proline-rich N-terminal region contains physiologically important binding sites for a ubiquitin ligase Itch and clathrin adaptor complex 3, but is likely disordered and dispensable for the kinase activity. The kinase domain can be divided into N-terminal and C-terminal lobes with the ATP binding groove and putative phosphatidylinositol binding pocket in between. The C-lobe of the kinase domain contains an additional lateral hydrophobic pocket with no distinct function assigned yet.
PI4K2A is important in lysosomal quality control. It is the first essential enzyme of the phosphoinositide-initiated membrane tethering and lipid transport (PITT) pathway for rapid lysosomal repair. Upon lysosomal membrane damage, PI4K2A is strongly recruited to lysosomes, leading to robust lysosomal PI4P production. Such lysosomal PI4K2A/PI4P signaling drives rapid lysosomal repair through extensive membrane contacts between the endoplasmic reticulum (ER) and damaged lysosomes as well as multiple ER-to-lysosomal lipid transfer processes.
Pi4k2a gene trap mouse show pre-mature aging and neurodegeneration, with increased lipofuscin accumulation. PI4K2A-deleted patients have complex and severe developmental problems along with neurodegeneration.
↑Wu B, Kitagawa K, Zhang NY, Liu B, Inagaki C (December 2004). "Pathophysiological concentrations of amyloid beta proteins directly inhibit rat brain and recombinant human type II phosphatidylinositol 4-kinase activity". Journal of Neurochemistry. 91 (5): 1164–1170. doi:10.1111/j.1471-4159.2004.02805.x. PMID15569259. S2CID36690417.
Further reading
Balla A, Balla T (July 2006). "Phosphatidylinositol 4-kinases: old enzymes with emerging functions". Trends in Cell Biology. 16 (7): 351–361. doi:10.1016/j.tcb.2006.05.003. PMID16793271.