Supplementary Material for: Cyclosporine-Induced Tubular Vacuolization: The Role of Bip/Grp78

Cyclosporine (CsA) nephrotoxicity shows characteristic tubular
vacuolization (TV) which is endoplasmic reticulum (ER) in origin.
However, the cellular events of CsA-induced TV and CsA-induced ER
remained unclear. The aim of the present study was to study the nature
of TV and the correlation to ER stress. Using proximal tubule NRK-52E
cells in vitro and an in vivo model of acute CsA nephrotoxicity, we
confirmed that CsA-induced TV was ER in origin and potentially
reversible. Our results showed that CsA-induced ER stress and involved
ER integrated stress response-related proteins (Bip/Grp78, ATF6, IRE1
and CHOP) but not cytoplasmic ER stress-related chaperones (HSP70,
HSP40, HSP27, HSP90 and HSP60). Importantly, Bip/Grp78 was overexpressed
on the membrane of TV and suppression of Bip/Grp78 blocked TV
formation. In addition, suppression of Bip/Grp78-enhanced CsA-induced
cell death and CsA-induced TV formation and Bip/Grp78 overexpression had
a characteristic striped pattern in the tubulointerstitium. In summary,
we demonstrate that CsA-induced TV was a potentially reversible process
in which Bip/Grp78 overexpression is essential for TV formation. It is
possible that Bip/Grp78 expression and TV formation may be involved in
cellular defense mechanism against CsA nephrotoxicity.