[Single-chain human anti-EGFR antibody/truncated protamine fusion protein carrying Hsp47 siRNA can induce apoptosis of human hepatic stellate cells]

Abstract

Objective: To construct a single-chain human anti-EGFR antibody (scFv) and truncated protamine (tP) fusion protein, ScFv/tP, carrying small interfering (si)RNA directed against the heat shock protein Hsp47, a collagen-binding glycoprotein, in order to evaluate the role Hsp47 in apoptosis of hepatic stellate cells.

Methods: A single chain of the human variable fragment was obtained by phage display and fused with the tP gene and with or without (negative control) the Hsp47 siRNA sequences. Following expression and purification of the scFv/tP fusion protein and the scFv/tPHsp47 siRNA fusion protein, internalization capabilities were tested in isolated human hepatic stellate cells and the QSG-7701 human hepatocyte cells with visualization by immunofluorescent staining. The DNA binding ability of the fusion proteins were verified by gel shift assay.Following ScFv/tP-Hsp47 siRNA fusion protein transfection into the human hepatic stellate cells, the levels of Hsp47 mRNA and protein expression were tested by RT-PCR and Western blotting; in addition, effects of siRNA-mediated silencing of Hsp47 on cell proliferation and apoptosis were analyzed by the cell counting kit (CCK)-8, flow cytometry and Western blot detection of the apoptosis marker poly (ADP-ribose) polymerase (PARP).

Results: Indirect immunofluorescence revealed that the ScFv/tP fusion proteins were internalized into human hepatic stellate cells but not into the QSG-7701 cells.The ScFv/tP-Hsp47 siRNA fusion protein caused reduced expression of Hsp47 mRNA and protein expression in the human hepatic stellate cells, as well as increased the cells' apoptosis remarkably.

Conclusion: The ScFv/tP fusion protein can be used as a transfection reagent to deliver Hsp47 siRNA into hepatic stellate cells and to mediate apoptosis via blockade of Hsp47 expression.