Lysyl oxidase-variant 2 (LOX-v2) colocalizes with promyelocytic leukemia-nuclear bodies in the nucleus

Lysyl oxidase-variant 2 (LOX-v2) is a novel variant of LOX that functions as an amine oxidase for the formation of collagen and elastin fibrils in the extracellular matrix (ECM). LOX-v2 lacks the N-terminal prepropeptide region of LOX but contains the C-terminal domains required for amine oxidase activity. To study the cellular localization of LOX-v2, we generated a recombinant construct of LOX-v2 with an epitope tag at the C-terminus and then transfected the recombinant construct into HEK293 cells. Upon ectopic expression, LOX-v2 showed much higher expression in the nucleus than in the cytoplasm. In coimmunofluorescence staining with subnuclear structures, LOX-v2 colocalized with the promyelocytic leukemia-nuclear bodies (PML-NBs). Further, the ectopic expression of LOX-v2 increased global SUMOylation in the nucleus. PML-NBs have been implicated in various cellular activities, including transcriptional regulation, DNA repair, cell cycle control, anti-viral response, and apoptosis. Our findings strongly indicate that LOX-v2 may be subject to different cellular processing from what LOX undergoes, playing a distinct functional role in the PML-NBs, beyond the cross-linking of the structural proteins.