Activation of PKC-βIin glomerular mesangial cells is associated with specific NF-κB subunit translocation

Abstract

Changes in expression and activity of protein kinase C (PKC) isoforms and early transcription factors may account for alterations in cell behavior seen in diabetes. We studied the expression of PKC-βIin rat glomerular mesangial cells (MCs) cultured in normal or high glucose and compared it with the temporal and spatial expression of dimeric transcription factor (NF-κB) p50 and p65. The results show that in unstimulated cells PKC-βIand NF-κB p50 are distributed in the cytosol and, on stimulation, their distribution is perinuclear and they are localized to the membrane. Serum-starved MCs cultured in high-glucose medium exhibit a predominantly cytosolic localization of PKC-βIand both p50 and p65 NF-κB. However, phorbol 12-myristate 13-acetate (PMA) stimulation of cells grown in the presence of high glucose resulted in membrane translocation of PKC-βIthat was associated with nuclear translocation of NF-κB p65, but not NF-κB p50. Moreover, the translocation to the nucleus for NF-κB p65 was significantly higher in MCs exposed to high glucose compared with those exposed to normal glucose. These observations indicate that the NF-κB p65, but not NF-κB p50, expression and translocation pattern mirrors that of PKC-βI, which may be one important pathway by which signaling is enhanced in the high-glucose state.