title: A putative mitochondrial calcium uniporter in A. fumigatus contributes to mitochondrial Ca(2+) homeostasis and stress responses.
abstract: Ca(2+) uptake into mitochondria plays a central role in cell physiology by stimulating ATP production, shaping cytosolic Ca(2+) transients and regulating cell survival or death. Although this system has been studied extensively in mammalian cells, the physiological implications of Ca(2+) uptake into mitochondria in fungal cells are still unknown. In this study, a bi-directional best-hit BLASTP search revealed that the genome of Aspergillus fumigatus encodes a homolog of a putative mitochondrial Ca(2+) uniporter (MCU) and a mitochondrial carrier protein AGC1/MICU1 homolog. Both putative homologs are mitochondrially localized and required for the response to azole and oxidative stress such that the loss of either McuA or AgcA results in reduced susceptibility to azole and oxidative stress, suggesting a role in environmental stress adaptation. Overexpressing mcuA restores the azole-resistance phenotype of the ΔagcA strain to wild-type levels, but not vice versa, indicating McuA plays a dominant role during these stress responses. Using a mitochondrially targeted version of the calcium-sensitive photoprotein aequorin, we found that only mcuA deletion leads to dysfunctional [Ca(2+)]mt and [Ca(2+)]c homeostasis, suggesting that McuA, but not AgcA, contributes to Ca(2+) uptake into mitochondria. Further point-mutation experiments combined with extracellular Ca(2+) chelator treatment verified that two predicted Ca(2+)-binding sites in McuA are required for Ca(2+) uptake into mitochondria and stress responses through the regulation of [Ca(2+)]c homeostasis.
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
authors.forename: Jinxing
authors.initials: J
authors.lastname: Song
authors.affiliation: School of Nursing, Qingdao Huanghai University, Shandong, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Liu
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Zhai
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Huang
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China. Electronic address: linglu@njnu.edu.cn.
authors.forename: Ling
authors.initials: L
authors.lastname: Lu
mesh_terms: D001232:Aspergillus fumigatus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D001393:Azoles / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D018384:Oxidative Stress; D013312:Stress, Physiological
chemical_list: D001393:Azoles; D015220:Calcium Channels; D005656:Fungal Proteins; C034703:mitochondrial calcium uniporter; D002118:Calcium
keywords: Aspergillus fumigatus; Calcium uniporter; Mitochondrial; Stress response