CONICET | Buscador de Institutos y Recursos Humanos

Poly-ADP-ribose-polymerase (PARP) family members which are competent to synthesize poly-ADP-ribose (PAR) exist both in cell nuclei and cytoplasm. While it is clear that nuclear PAR modulates chromatin compaction, affecting nuclear functions (gene expression, DNA repair), PAR cytoplasmic distributions and functions are still ill-defined. In the present work, we have examined through immunofluorescence and confocal microscopy, the subcellular localization of PAR in an epithelial monkey kidney cell line (VERO). PAR was associated to cortical actin and vinculin in the epithelial belt. Cells seeded in the presence of the PARP inhibitors 3 aminobenzamide, PJ34 and XAV939 displayed alterations in cell shape and even stalled cell adhesion. Moreover, biotinylated-NAD+ incorporation to cells electroporated just before seeding disclosed polarized conspicuous NAD+-rich vesicle traffic towards the nascent junctions. Comparison of the effects of PARP inhibitors strongly suggested the involvement of tankyrases (probably TNK1) in PAR belt synthesis. Accordingly, PAR belt synthesis was impeded by the extracellular Ca2+-chelator EGTA, which blocks E-cadherin dependent cell-cell adhesion while hampering TNK1 association with the plasma membrane. In this situation, actin cytoskeleton was also affected. Conversely, when actin polymerization was prevented by cytochalasin D, the PAR belt was disrupted. We propose for the first time that cytoplasmic PAR would be involved in adherens junction complexes that connect E-cadherin, α- and β-catenin, vinculin and actin microfilaments in polarized epithelial cells. A model relating TNK1, Wnt signaling and PAR subcellular localization and dynamics is also suggested. The present work expands our perspectives regarding PAR functions, with deep implications in pathological situations.