Establishment of canine macrophages stably expressing GFP-tagged canine LC3 protein for effectively detecting autophagy.

Autophagy plays a crucial role in eliminating protein aggregates, damaged organelles and invading pathogens. Genetically engineered cell line stably expressing green fluorescent protein (GFP)-tagged microtubule-associated protein light chain 3 (LC3) is extensively used to test autophagy through observing GFP puncta formation in the cells by fluorescence imaging. However, canine LC3 (cLC3) gene has not been cloned, therefore, GFP-tagged canine LC3 (GFP-cLC3) detection system has not been established. To generate GFP-cLC3 stably expressing canine-derived macrophages, the cLC3 cDNA was first amplified by RT-PCR and inserted into pEGFP-C1 plasmid to create GFP-cLC3 gene fusion. This genetic element was then transducted into canine macrophages mediated by lentivirus vector to generate the canine macrophages stably expressing fusion protein. Results showed that the sequence of cLC3 cloned in this study is highly homologous with other animals (80-95% homology). Phenotypic and functional analysis of these engineered cells revealed that GFP-cLC3 was indeed stably expressed and rapamycin or starvation can effectively induce GFP puncta formation in the cells, indicative of autophagosome formation. These GFP-cLC3-expressing cells may thus be useful to study autophagy in canine.