Madin-Darby bovine kidney cells stably expressing microtubule-associated protein 1 light chain 3B ( LC3B ) with green fluorescent protein ( GFP ) ( GFP-LC3-MDBK cells ) and autophagy-deficient MDBKs ( shBCN1-MDBK Yulong Zhou and Yachao Ren have contributed equally to this work.