The cytoplasmic protein Pacsin 2 in kidney development and injury repair.

The protein kinase C and casein kinase 2 substrate in neurons (Pacsin) is a subfamily of membrane-binding proteins that participates in vesicle trafficking and cytoskeleton organization. Here, we studied Pacsin 2 in kidney development and repair following injury. In the postnatal developing kidneys, Pacsin 2 was found to be expressed in both ureteric bud- and mesenchyme-derived structures including proximal and distal tubules, Bowman's capsule, and the glomerular tuft. In the adult kidney, its expression was decreased in proximal tubules but increased in glomerular tuft when compared to that in the developing kidneys. Interestingly, Pacsin 2 expression was significantly upregulated during the repair phase after ischemia-reperfusion injury, especially on the apical brush border of proximal tubules that experienced massive damage. Pacsin 2 localized to the primary cilia of renal epithelial cells. Knockdown of Pacsin 2 by shRNA did not affect the cell cycle or cell polarity; however, it increased the length of primary cilia, and resulted in significant tubulogenic defects in three-dimensional cell culture. Thus, we propose that Pacsin 2 contributes to kidney development and repair in a nephron-specific manner.