title: Extracellular calcium influx promotes antibacterial autophagy in Escherichia coli infected murine macrophages via CaMKKβ dependent activation of ERK1/2, AMPK and FoxO1.
abstract: Autophagy induction has been found as an alternative mechanism for ultimate elimination of invaded bacteria in innate immune cells. However, underlying mechanisms for the regulation of antibacterial autophagy require further elucidation. The present study mainly explores calcium dependent regulation of autophagy and its contribution to bactericidal activity in Escherichia coli (E. coli) infected murine macrophages. In this study, E. coli was shown to increase cellular calcium levels by triggering extracellular calcium influx in murine bone marrow derived macrophages. The elevated calcium was required for autophagy and bactericidal activity against E. coli, as extracellular calcium depletion or inhibition of calcium influx suppressed E. coli induced Beclin1 and LC3B expression, dampened LC3B puncta or LC3I to LC3II conversion and impaired intracellular E. coli degradation. Then CaMKKβ was identified as activated by E. coli induced calcium influx and chemical inhibition or RNAi knockdown of CaMKKβ abolished calcium mediated antibacterial autophagy. CaMKKβ was demonstrated to activate signaling pathways involving ERK, AMPK and FoxO1 and RNAi knockdown of these molecules also dampened the antibacterial autophagy against E. coli. In summary, we demonstrate a new mechanism of calcium dependent antibacterial strategy in E. coli infected macrophages, which requires autophagy enhancement mediated by activation of CaMKKβ, ERK, AMPK and FoxO1.
authors.affiliation: Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.affiliation: Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.affiliation: Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors.forename: Yuanfeng
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Chen
authors.affiliation: Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, College of Pharmacy, Third Military Medical University, Chongqing, 400038, China. Electronic address: zhouh64@163.com.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China. Electronic address: zhengj99219@163.com.
authors.forename: Jiang
authors.initials: J
authors.lastname: Zheng
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D001343:Autophagy / Q000502:physiology; D002118:Calcium / Q000493:pharmacokinetics*; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism*; D004926:Escherichia coli / Q000166:cytology / Q000502:physiology*; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology; D008264:Macrophages / Q000166:cytology / Q000382:microbiology* / Q000502:physiology*; D051379:Mice
chemical_list: D016207:Cytokines; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D055372:AMP-Activated Protein Kinases; D002118:Calcium
keywords: Antibacterial autophagy; CaMKKβ; Calcium; Escherichia coli; Macrophage