title: Porcine Circovirus Type 2 Activates CaMMKβ to Initiate Autophagy in PK-15 Cells by Increasing Cytosolic Calcium.
abstract: Porcine circovirus type 2 (PCV2) induces autophagy via the 5' adenosine monophosphate-activated protein kinase (AMPK)/extracellular signal-regulated kinase (ERK)/tuberous sclerosis complex 2 (TSC2)/mammalian target of rapamycin (mTOR) pathway in pig kidney PK-15 cells. However, the underlying mechanisms of AMPK activation in autophagy induction remain unknown. With specific inhibitors and RNA interference (RNAi), we show that PCV2 infection upregulated calcium/calmodulin-dependent protein kinase kinase-beta (CaMKKβ) by increasing cytosolic Ca(2+) via inositol 1,4,5-trisphosphate receptor (IP3R). Elevation of cytosolic calcium ion (Ca(2+)) did not seem to involve inositol 1,4,5-trisphosphate (IP3) release from phosphatidylinositol 4,5-bisphosphate (PIP2) by phosphoinositide phospholipase C-gamma (PLC-γ). CaMKKβ then activated both AMPK and calcium/calmodulin-dependent protein kinase I (CaMKI). PCV2 employed CaMKI and Trp-Asp (WD) repeat domain phosphoinositide-interacting protein 1 (WIPI1) as another pathway additional to AMPK signaling in autophagy initiation. Our findings could help better understanding of the signaling pathways of autophagy induction as part of PCV2 pathogenesis. Further research is warranted to study if PCV2 interacts directly with IP3R or indirectly with the molecules that antagonize IP3R activity responsible for increased cytosolic Ca(2+) both in PK-15 cells and PCV2-targeted primary cells from pigs.
authors.affiliation: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou 310058, China. guzi.123@163.com.
authors.forename: Yuanxing
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou 310058, China. qibaozhu@yeah.net.
authors.forename: Baozhu
authors.initials: B
authors.lastname: Qi
authors.affiliation: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou 310058, China. yszhou@zju.edu.cn.
authors.forename: Yingshan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou 310058, China. cqrcxwj@163.com.
authors.forename: Xiaowu
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou 310058, China. zhangxian073@163.com.
authors.forename: Xian
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou 310058, China. xlli@zju.edu.cn.
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Li
authors.affiliation: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang University, Hangzhou 310058, China. whfang@zju.edu.cn.
authors.forename: Weihuan
authors.initials: W
authors.lastname: Fang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D001343:Autophagy; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase / Q000378:metabolism*; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1 / Q000378:metabolism; D002460:Cell Line; D017925:Circovirus / Q000472:pathogenicity*; D004847:Epithelial Cells / Q000502:physiology / Q000821:virology; D054884:Host-Pathogen Interactions; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D013552:Swine
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; D055372:AMP-Activated Protein Kinases; D002118:Calcium
keywords: Ca2+ signaling; autophagy; pathogenesis; porcine circovirus 2