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Ding X, Yu Q, Xu N, Wang Y, Cheng X, Qian K, Zhao Q, Zhang B, Xing L, Li M. Ecm7, a regulator of HACS, functions in calcium homeostasis maintenance, oxidative stress response and hyphal development in Candida albicans. Fungal Genet Biol 2013; 57:23-32. [PMID: 23769872 DOI: 10.1016/j.fgb.2013.05.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 05/04/2013] [Accepted: 05/09/2013] [Indexed: 10/26/2022]
Abstract
Calcium is a universal messenger that translates diverse environmental stresses and developmental cues into specific cellular and developmental responses. In yeast, Cch1 and Mid1 function as part of a high affinity Ca²⁺ influx system (HACS) that becomes activated rapidly in response to sudden stimuli. Here, we report that Ecm7, a regulator of HACS, plays important roles in calcium homeostasis maintenance, oxidative stress response and hyphal development in Candida albicans. Disruption of ECM7 led to increased sensitivity to calcium-depleted conditions. Flow cytometry analysis revealed that Ecm7 mediated Ca²⁺ influx under high pH shock. Cycloheximide chase experiments further showed that MID1 deletion significantly decreased the stability of Ecm7. We also provided evidences that ecm7Δ/Δ cells were hypersensitive to oxidative stress. ECM7 deletion induced the degradation of Cap1 when exposed to H₂O₂ treatment. Besides, the ecm7Δ/Δ mutant showed a defect in hyphal development, which was accompanied with the decreased expression of hyphal related gene HWP1. Though subsequent experiments revealed that the ecm7Δ/Δ mutant showed similar virulence to the wild-type strain, the ability of invasion and diffusion of the mutant in mouse kidneys decreased. Taken together, Ecm7 plays important roles in the adaptation and pathogenicity of C. albicans.
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Affiliation(s)
- Xiaohui Ding
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
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Teng J, Iida K, Imai A, Nakano M, Tada T, Iida H. Hyperactive and hypoactive mutations in Cch1, a yeast homologue of the voltage-gated calcium-channel pore-forming subunit. Microbiology (Reading) 2013; 159:970-979. [DOI: 10.1099/mic.0.064030-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Jinfeng Teng
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
| | - Kazuko Iida
- Biomembrane Laboratory, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Ayumi Imai
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
| | - Masataka Nakano
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
| | - Tomoko Tada
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
| | - Hidetoshi Iida
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
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Cch1 and Mid1 are functionally required for vegetative growth under low-calcium conditions in the phytopathogenic ascomycete Botrytis cinerea. EUKARYOTIC CELL 2013; 12:712-24. [PMID: 23475703 DOI: 10.1128/ec.00338-12] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In the filamentous phytopathogen Botrytis cinerea, the Ca(2+)/calcineurin signaling cascade has been shown to play an important role in fungal growth, differentiation, and virulence. This study deals with the functional characterization of two components of this pathway, the putative calcium channel proteins Cch1 and Mid1. The cch1 and mid1 genes were deleted, and single and double knockout mutants were analyzed during different stages of the fungal life cycle. Our data indicate that Cch1 and Mid1 are functionally required for vegetative growth under conditions of low extracellular calcium, since the growth of both deletion mutants is strongly impaired when they are exposed to the Ca(2+)-chelating agents EGTA and 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). The impact of external Ca(2+) was investigated by supplementing with CaCl(2) and the ionophore A23187, both of which resulted in elevated growth for all mutants. However, deletion of either gene had no impact on germination, sporulation, hyphal morphology, or virulence. By use of the aequorin reporter system to measure intracellular calcium levels, no differences between the mutant strains and the wild type were obtained. Localization studies revealed a subcellular distribution of the Mid1-green fluorescent protein (GFP) fusion protein in network-like filaments, probably the endoplasmic reticulum (ER) membranes, indicating that Mid1 is not a plasma membrane-located calcium channel in B. cinerea.
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Bodvard K, Jörhov A, Blomberg A, Molin M, Käll M. The yeast transcription factor Crz1 is activated by light in a Ca2+/calcineurin-dependent and PKA-independent manner. PLoS One 2013; 8:e53404. [PMID: 23335962 PMCID: PMC3546054 DOI: 10.1371/journal.pone.0053404] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 11/28/2012] [Indexed: 11/19/2022] Open
Abstract
Light in the visible range can be stressful to non-photosynthetic organisms. The yeast Saccharomyces cerevisiae has earlier been reported to respond to blue light via activation of the stress-regulated transcription factor Msn2p. Environmental changes also induce activation of calcineurin, a Ca(2+)/calmodulin dependent phosphatase, which in turn controls gene transcription by dephosphorylating the transcription factor Crz1p. We investigated the connection between cellular stress caused by blue light and Ca(2+) signalling in yeast by monitoring the nuclear localization dynamics of Crz1p, Msn2p and Msn4p. The three proteins exhibit distinctly different stress responses in relation to light exposure. Msn2p, and to a lesser degree Msn4p, oscillate rapidly between the nucleus and the cytoplasm in an apparently stochastic fashion. Crz1p, in contrast, displays a rapid and permanent nuclear localization induced by illumination, which triggers Crz1p-dependent transcription of its target gene CMK2. Moreover, increased extracellular Ca(2+) levels stimulates the light-induced responses of all three transcription factors, e.g. Crz1p localizes much quicker to the nucleus and a larger fraction of cells exhibits permanent Msn2p nuclear localization at higher Ca(2+) concentration. Studies in mutants lacking Ca(2+) transporters indicate that influx of extracellular Ca(2+) is crucial for the initial stages of light-induced Crz1p nuclear localization, while mobilization of intracellular Ca(2+) stores appears necessary for a sustained response. Importantly, we found that Crz1p nuclear localization is dependent on calcineurin and the carrier protein Nmd5p, while not being affected by increased protein kinase A activity (PKA), which strongly inhibits light-induced nuclear localization of Msn2/4p. We conclude that the two central signalling pathways, cAMP-PKA-Msn2/4 and Ca(2+)-calcineurin-Crz1, are both activated by blue light illumination.
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Affiliation(s)
- Kristofer Bodvard
- Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
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Allen A, Islamovic E, Kaur J, Gold S, Shah D, Smith TJ. The virally encoded killer proteins from Ustilago maydis. FUNGAL BIOL REV 2013. [DOI: 10.1016/j.fbr.2012.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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56
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Activation of an essential calcium signaling pathway in Saccharomyces cerevisiae by Kch1 and Kch2, putative low-affinity potassium transporters. EUKARYOTIC CELL 2012. [PMID: 23204190 DOI: 10.1128/ec.00299-12] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the budding yeast Saccharomyces cerevisiae, mating pheromones activate a high-affinity Ca(2+) influx system (HACS) that activates calcineurin and is essential for cell survival. Here we identify extracellular K(+) and a homologous pair of transmembrane proteins, Kch1 and Kch2 (Prm6), as necessary components of the HACS activation mechanism. Expression of Kch1 and especially Kch2 was strongly induced during the response to mating pheromones. When forcibly overexpressed, Kch1 and Kch2 localized to the plasma membrane and activated HACS in a fashion that depended on extracellular K(+) but not pheromones. They also promoted growth of trk1 trk2 mutant cells in low K(+) environments, suggesting they promote K(+) uptake. Voltage-clamp recordings of protoplasts revealed diminished inward K(+) currents in kch1 kch2 double-mutant cells relative to the wild type. Conversely, heterologous expression of Kch1 in HEK293T cells caused the appearance of inwardly rectifying K(+) currents. Collectively, these findings suggest that Kch1 and Kch2 directly promote K(+) influx and that HACS may electrochemically respond to K(+) influx in much the same way as the homologous voltage-gated Ca(2+) channels in most animal cell types.
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Activity of the calcium channel pore Cch1 is dependent on a modulatory region of the subunit Mid1 in Cryptococcus neoformans. EUKARYOTIC CELL 2012; 12:142-50. [PMID: 23175710 DOI: 10.1128/ec.00130-12] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Calcium (Ca(2+))-mediated signaling events in fungal pathogens such as Cryptococcus neoformans are central to physiological processes, including those that mediate stress responses and promote virulence. The Cch1-Mid1 channel (CMC) represents the only high-affinity Ca(2+) channel in the plasma membrane of fungal cells; consequently, cryptococci cannot survive in low-Ca(2+) environments in the absence of CMC. Previous electrophysiological characterization revealed that Cch1, the predicted channel pore, and Mid1, a binding partner of Cch1, function as a store-operated Ca(2+)-selective channel gated by depletion of endoplasmic reticulum (ER) Ca(2+) stores. Cryptococci lacking CMC did not survive ER stress, indicating its critical role in restoring Ca(2+) homeostasis. Despite the requirement for Mid1 in promoting Ca(2+) influx via Cch1, identification of the role of Mid1 remains elusive. Here we show that the C-terminal tail of Mid1 is a modulatory region that impinges on Cch1 channel activity directly and mediates the trafficking of Mid1 to the plasma membrane. This region consists of the last 24 residues of Mid1, and the functional expression of Mid1 in a human embryonic cell line (HEK293) and in C. neoformans is dependent on this domain. Substitutions of arginine (R619A) or cysteine (C621A) in the modulatory region failed to target Mid1 to the plasma membrane and prevented CMC activity. Interestingly, loss of a predicted protein kinase C (PKC)-phosphorylated serine residue (S605A) had no effect on Mid1 trafficking but did alter the kinetics of Cch1 channel activity. Thus, establishment of Ca(2+) homeostasis in C. neoformans is dependent on a modulatory domain of Mid1.
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Bowman BJ, Abreu S, Johl JK, Bowman EJ. The pmr gene, encoding a Ca2+-ATPase, is required for calcium and manganese homeostasis and normal development of hyphae and conidia in Neurospora crassa. EUKARYOTIC CELL 2012; 11:1362-70. [PMID: 22983986 PMCID: PMC3486030 DOI: 10.1128/ec.00105-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 09/06/2012] [Indexed: 12/17/2022]
Abstract
The pmr gene is predicted to encode a Ca(2+)-ATPase in the secretory pathway. We examined two strains of Neurospora crassa that lacked PMR: the Δpmr strain, in which pmr was completely deleted, and pmr(RIP), in which the gene was extensively mutated. Both strains had identical, complex phenotypes. Compared to the wild type, these strains required high concentrations of calcium or manganese for optimal growth and had highly branched, slow-growing hyphae. They conidiated poorly, and the shape and size of the conidia were abnormal. Calcium accumulated in the Δpmr strains to only 20% of the wild-type level. High concentrations of MnCl(2) (1 to 5 mM) in growth medium partially suppressed the morphological defects but did not alter the defect in calcium accumulation. The Δpmr Δnca-2 double mutant (nca-2 encodes a Ca(2+)-ATPase in the plasma membrane) accumulated 8-fold more calcium than the wild type, and the morphology of the hyphae was more similar to that of wild-type hyphae. Previous experiments failed to show a function for nca-1, which encodes a SERCA-type Ca(2+)-ATPase in the endoplasmic reticulum (B. J. Bowman, S. Abreu, E. Margolles-Clark, M. Draskovic, and E. J. Bowman, Eukaryot. Cell 10:654-661, 2011). The pmr(RIP) Δnca-1 double mutant accumulated small amounts of calcium, like the Δpmr strain, but exhibited even more extreme morphological defects. Thus, PMR can apparently replace NCA-1 in the endoplasmic reticulum, but NCA-1 cannot replace PMR. The morphological defects in the Δpmr strain are likely caused, in part, by insufficient concentrations of calcium and manganese in the Golgi compartment; however, PMR is also needed to accumulate normal levels of calcium in the whole cell.
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Affiliation(s)
- Barry J Bowman
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, CA, USA.
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Wang S, Cao J, Liu X, Hu H, Shi J, Zhang S, Keller NP, Lu L. Putative calcium channels CchA and MidA play the important roles in conidiation, hyphal polarity and cell wall components in Aspergillus nidulans. PLoS One 2012; 7:e46564. [PMID: 23071589 PMCID: PMC3470553 DOI: 10.1371/journal.pone.0046564] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 08/31/2012] [Indexed: 11/25/2022] Open
Abstract
Although the high affinity Ca2+ channel, Cch1, and its subunit Mid1 have been investigated and evaluated in yeast and some of filamentous fungi, little is known about the function of their homologs in the Aspergilli. Here, we have functionally characterized the yeast homologs, CchA and MidA, in Aspergillus nidulans using conditional and null deletion mutants. CchA and MidA not only have functional benefits of fast growth, which is consistent with Cch1 and Mid1 in yeast, but also have unique and complex roles in regulating conidiation, hyphal polarity and cell wall components in low-calcium environments. The defect of CchA or MidA resulted in a sharp reduction in the number of conidiospores, accompanied by abnormal metulae, and undeveloped-phialides at a higher density of inoculum. Most interestingly, these conidiation defects in mutants can, remarkably, be rescued either by extra-cellular Ca2+ in a calcineurin-dependent way or by osmotic stress in a calcineurin-independent way. Moreover, the fact that the phenotypic defects are not exacerbated by the presence of the double deletion, together with the Y2H assay, indicates that CchA and MidA may form a complex to function together. Our findings suggest that the high-affinity Ca2+ channel may represent a viable and completely unexplored avenue to reduce conidiation in the Aspergilli.
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Affiliation(s)
- Sha Wang
- Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences; Nanjing Normal University, Nanjing, China
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Prole DL, Taylor CW. Identification and analysis of cation channel homologues in human pathogenic fungi. PLoS One 2012; 7:e42404. [PMID: 22876320 PMCID: PMC3410928 DOI: 10.1371/journal.pone.0042404] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 07/05/2012] [Indexed: 01/08/2023] Open
Abstract
Fungi are major causes of human, animal and plant disease. Human fungal infections can be fatal, but there are limited options for therapy, and resistance to commonly used anti-fungal drugs is widespread. The genomes of many fungi have recently been sequenced, allowing identification of proteins that may become targets for novel therapies. We examined the genomes of human fungal pathogens for genes encoding homologues of cation channels, which are prominent drug targets. Many of the fungal genomes examined contain genes encoding homologues of potassium (K+), calcium (Ca2+) and transient receptor potential (Trp) channels, but not sodium (Na+) channels or ligand-gated channels. Some fungal genomes contain multiple genes encoding homologues of K+ and Trp channel subunits, and genes encoding novel homologues of voltage-gated Kv channel subunits are found in Cryptococcus spp. Only a single gene encoding a homologue of a plasma membrane Ca2+ channel was identified in the genome of each pathogenic fungus examined. These homologues are similar to the Cch1 Ca2+ channel of Saccharomyces cerevisiae. The genomes of Aspergillus spp. and Cryptococcus spp., but not those of S. cerevisiae or the other pathogenic fungi examined, also encode homologues of the mitochondrial Ca2+ uniporter (MCU). In contrast to humans, which express many K+, Ca2+ and Trp channels, the genomes of pathogenic fungi encode only very small numbers of K+, Ca2+ and Trp channel homologues. Furthermore, the sequences of fungal K+, Ca2+, Trp and MCU channels differ from those of human channels in regions that suggest differences in regulation and susceptibility to drugs.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom.
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Liebeskind BJ, Hillis DM, Zakon HH. Phylogeny unites animal sodium leak channels with fungal calcium channels in an ancient, voltage-insensitive clade. Mol Biol Evol 2012; 29:3613-6. [PMID: 22821012 DOI: 10.1093/molbev/mss182] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Proteins in the superfamily of voltage-gated ion channels mediate behavior across the tree of life. These proteins regulate the movement of ions across cell membranes by opening and closing a central pore that controls ion flow. The best-known members of this superfamily are the voltage-gated potassium, calcium (Ca(v)), and sodium (Na(v)) channels, which underlie impulse conduction in nerve and muscle. Not all members of this family are opened by changes in voltage, however. NALCN (NA(+) leak channel nonselective) channels, which encode a voltage-insensitive "sodium leak" channel, have garnered a growing interest. This study examines the phylogenetic relationship among Na(v)/Ca(v) voltage-gated and voltage-insensitive channels in the eukaryotic group Opisthokonta, which includes animals, fungi, and their unicellular relatives. We show that NALCN channels diverged from voltage-gated channels before the divergence of fungi and animals and that the closest relatives of NALCN channels are fungal calcium channels, which they functionally resemble.
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Affiliation(s)
- Benjamin J Liebeskind
- Section of Integrative Biology and Center for Computational Biology and Bioinformatics, University of Texas, USA.
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Kurusu T, Yamanaka T, Nakano M, Takiguchi A, Ogasawara Y, Hayashi T, Iida K, Hanamata S, Shinozaki K, Iida H, Kuchitsu K. Involvement of the putative Ca²⁺-permeable mechanosensitive channels, NtMCA1 and NtMCA2, in Ca²⁺ uptake, Ca²⁺-dependent cell proliferation and mechanical stress-induced gene expression in tobacco (Nicotiana tabacum) BY-2 cells. JOURNAL OF PLANT RESEARCH 2012; 125:555-68. [PMID: 22080252 DOI: 10.1007/s10265-011-0462-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 10/24/2011] [Indexed: 05/18/2023]
Abstract
To gain insight into the cellular functions of the mid1-complementing activity (MCA) family proteins, encoding putative Ca²⁺-permeable mechanosensitive channels, we isolated two MCA homologs of tobacco (Nicotiana tabacum) BY-2 cells, named NtMCA1 and NtMCA2. NtMCA1 and NtMCA2 partially complemented the lethality and Ca²⁺ uptake defects of yeast mutants lacking mechanosensitive Ca²⁺ channel components. Furthermore, in yeast cells overexpressing NtMCA1 and NtMCA2, the hypo-osmotic shock-induced Ca²⁺ influx was enhanced. Overexpression of NtMCA1 or NtMCA2 in BY-2 cells enhanced Ca²⁺ uptake, and significantly alleviated growth inhibition under Ca²⁺ limitation. NtMCA1-overexpressing BY-2 cells showed higher sensitivity to hypo-osmotic shock than control cells, and induced the expression of the touch-inducible gene, NtERF4. We found that both NtMCA1-GFP and NtMCA2-GFP were localized at the plasma membrane and its interface with the cell wall, Hechtian strands, and at the cell plate and perinuclear vesicles of dividing cells. NtMCA2 transcript levels fluctuated during the cell cycle and were highest at the G1 phase. These results suggest that NtMCA1 and NtMCA2 play roles in Ca²⁺-dependent cell proliferation and mechanical stress-induced gene expression in BY-2 cells, by regulating the Ca²⁺ influx through the plasma membrane.
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Affiliation(s)
- Takamitsu Kurusu
- Department of Applied Biological Science, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
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Role of Fig1, a component of the low-affinity calcium uptake system, in growth and sexual development of filamentous fungi. EUKARYOTIC CELL 2012; 11:978-88. [PMID: 22635922 DOI: 10.1128/ec.00007-12] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The function of Fig1, a transmembrane protein of the low-affinity calcium uptake system (LACS) in fungi, was examined for its role in the growth and development of the plant pathogen Fusarium graminearum. The Δfig1 mutants failed to produce mature perithecia, and sexual development was halted prior to the formation of perithecium initials. The loss of Fig1 function also resulted in a reduced vegetative growth rate. Macroconidium production was reduced 70-fold in the Δfig1 mutants compared to the wild type. The function of the high-affinity calcium uptake system (HACS), comprised of the Ca(2+) channels Mid1 and Cch1, was previously characterized for F. graminearum. To better understand the roles of the LACS and the HACS, Δfig1 Δmid1, Δfig1 Δcch1, and Δfig1 Δmid1 Δcch1 double and triple mutants were generated, and the phenotypes of these mutants were more severe than those of the Δfig1 mutants. Pathogenicity on wheat was unaffected for the Δfig1 mutants, but the Δfig1 Δmid1, Δfig1 Δcch1, and Δfig1 Δmid1 Δcch1 mutants, lacking both LACS and HACS functions, had reduced pathogenicity. Additionally, Δfig1 mutants of Neurospora crassa were examined and did not affect filamentous growth or female fertility in a Δfig1 mating type A strain, but the Δfig1 mating type a strain failed to produce fertile fruiting bodies. These results are the first report of Fig1 function in filamentous ascomycetes and expand its role to include complex fruiting body and ascus development.
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Kim H, Kim A, Cunningham KW. Vacuolar H+-ATPase (V-ATPase) promotes vacuolar membrane permeabilization and nonapoptotic death in stressed yeast. J Biol Chem 2012; 287:19029-39. [PMID: 22511765 DOI: 10.1074/jbc.m112.363390] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stress in the endoplasmic reticulum caused by tunicamycin, dithiothreitol, and azole-class antifungal drugs can induce nonapoptotic cell death in yeasts that can be blocked by the action of calcineurin (Cn), a Ca(2+)-dependent serine/threonine protein phosphatase. To identify additional factors that regulate nonapoptotic cell death in yeast, a collection of gene knock-out mutants was screened for mutants exhibiting altered survival rates. The screen revealed an endocytic protein (Ede1) that can function upstream of Ca(2+)/calmodulin-dependent protein kinase 2 (Cmk2) to suppress cell death in parallel to Cn. The screen also revealed the vacuolar H(+)-ATPase (V-ATPase), which acidifies the lysosome-like vacuole. The V-ATPase performed its death-promoting functions very soon after imposition of the stress and was not required for later stages of the cell death program. Cn did not inhibit V-ATPase activities but did block vacuole membrane permeabilization (VMP), which occurred at late stages of the cell death program. All of the other nondying mutants identified in the screens blocked steps before VMP. These findings suggest that VMP is the lethal event in dying yeast cells and that fungi may employ a mechanism of cell death similar to the necrosis-like cell death of degenerating neurons.
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Affiliation(s)
- Hyemin Kim
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA
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Yarotskyy V, Gao G, Peterson BZ, Elmslie KS. Domain III regulates N-type (CaV2.2) calcium channel closing kinetics. J Neurophysiol 2011; 107:1942-51. [PMID: 22205645 DOI: 10.1152/jn.00993.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ca(V)2.2 (N-type) and Ca(V)1.2 (L-type) calcium channels gate differently in response to membrane depolarization, which is critical to the unique physiological functions mediated by these channels. We wondered if the source for these differences could be identified. As a first step, we examined the effect of domain exchange between N-type and L-type channels on activation-deactivation kinetics, which were significantly different between these channels. Kinetic analysis of chimeric channels revealed N-channel-like deactivation for all chimeric channels containing N-channel domain III, while activation appeared to be a more distributed function across domains. This led us to hypothesize that domain III was an important regulator of N-channel closing. This idea was further examined with R-roscovitine, which is a trisubstituted purine that slows N-channel deactivation by exclusively binding to activated N-channels. L-channels lack this response to roscovitine, which allowed us to use N-L chimeras to test the role of domain III in roscovitine modulation of N-channel deactivation. In support of our hypothesis, all chimeric channels containing the N-channel domain III responded to roscovitine with slowed deactivation, while those chimeric channels with L-channel domain III did not. Thus a combination of kinetic and pharmacological evidence supports the hypothesis that domain III is an important regulator of N-channel closing. Our results support specialization of gating functions among calcium channel domains.
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Affiliation(s)
- Viktor Yarotskyy
- Dept. of Pharmacology, Kirksville Coll. of Osteopathic Medicine, AT Still Univ., 800 W. Jefferson St., Kirksville, MO 63501, USA
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Lanthaler K, Bilsland E, Dobson PD, Moss HJ, Pir P, Kell DB, Oliver SG. Genome-wide assessment of the carriers involved in the cellular uptake of drugs: a model system in yeast. BMC Biol 2011; 9:70. [PMID: 22023736 PMCID: PMC3280192 DOI: 10.1186/1741-7007-9-70] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 10/24/2011] [Indexed: 01/10/2023] Open
Abstract
Background The uptake of drugs into cells has traditionally been considered to be predominantly via passive diffusion through the bilayer portion of the cell membrane. The recent recognition that drug uptake is mostly carrier-mediated raises the question of which drugs use which carriers. Results To answer this, we have constructed a chemical genomics platform built upon the yeast gene deletion collection, using competition experiments in batch fermenters and robotic automation of cytotoxicity screens, including protection by 'natural' substrates. Using these, we tested 26 different drugs and identified the carriers required for 18 of the drugs to gain entry into yeast cells. Conclusions As well as providing a useful platform technology, these results further substantiate the notion that the cellular uptake of pharmaceutical drugs normally occurs via carrier-mediated transport and indicates that establishing the identity and tissue distribution of such carriers should be a major consideration in the design of safe and effective drugs.
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Affiliation(s)
- Karin Lanthaler
- School of Chemistry, University of Manchester, Manchester, UK
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67
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Prole DL, Taylor CW. Identification of intracellular and plasma membrane calcium channel homologues in pathogenic parasites. PLoS One 2011; 6:e26218. [PMID: 22022573 PMCID: PMC3194816 DOI: 10.1371/journal.pone.0026218] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 09/22/2011] [Indexed: 11/29/2022] Open
Abstract
Ca2+ channels regulate many crucial processes within cells and their abnormal activity can be damaging to cell survival, suggesting that they might represent attractive therapeutic targets in pathogenic organisms. Parasitic diseases such as malaria, leishmaniasis, trypanosomiasis and schistosomiasis are responsible for millions of deaths each year worldwide. The genomes of many pathogenic parasites have recently been sequenced, opening the way for rational design of targeted therapies. We analyzed genomes of pathogenic protozoan parasites as well as the genome of Schistosoma mansoni, and show the existence within them of genes encoding homologues of mammalian intracellular Ca2+ release channels: inositol 1,4,5-trisphosphate receptors (IP3Rs), ryanodine receptors (RyRs), two-pore Ca2+ channels (TPCs) and intracellular transient receptor potential (Trp) channels. The genomes of Trypanosoma, Leishmania and S. mansoni parasites encode IP3R/RyR and Trp channel homologues, and that of S. mansoni additionally encodes a TPC homologue. In contrast, apicomplexan parasites lack genes encoding IP3R/RyR homologues and possess only genes encoding TPC and Trp channel homologues (Toxoplasma gondii) or Trp channel homologues alone. The genomes of parasites also encode homologues of mammalian Ca2+influx channels, including voltage-gated Ca2+ channels and plasma membrane Trp channels. The genome of S. mansoni also encodes Orai Ca2+ channel and STIM Ca2+ sensor homologues, suggesting that store-operated Ca2+ entry may occur in this parasite. Many anti-parasitic agents alter parasite Ca2+ homeostasis and some are known modulators of mammalian Ca2+ channels, suggesting that parasite Ca2+ channel homologues might be the targets of some current anti-parasitic drugs. Differences between human and parasite Ca2+ channels suggest that pathogen-specific targeting of these channels may be an attractive therapeutic prospect.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom.
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68
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Cunningham KW. Acidic calcium stores of Saccharomyces cerevisiae. Cell Calcium 2011; 50:129-38. [PMID: 21377728 DOI: 10.1016/j.ceca.2011.01.010] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 01/25/2011] [Accepted: 01/31/2011] [Indexed: 02/06/2023]
Abstract
Fungi and animals constitute sister kingdoms in the eukaryotic domain of life. The major classes of transporters, channels, sensors, and effectors that move and respond to calcium ions were already highly networked in the common ancestor of fungi and animals. Since that time, some key components of the network have been moved, altered, relocalized, lost, or duplicated in the fungal and animal lineages and at the same time some of the regulatory circuitry has been dramatically rewired. Today the calcium transport and signaling networks in fungi provide a fresh perspective on the scene that has emerged from studies of the network in animal cells. This review provides an overview of calcium signaling networks in fungi, particularly the model yeast Saccharomyces cerevisiae, with special attention to the dominant roles of acidic calcium stores in fungal cell physiology.
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Affiliation(s)
- Kyle W Cunningham
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
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69
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Mid1, a mechanosensitive calcium ion channel, affects growth, development, and ascospore discharge in the filamentous fungus Gibberella zeae. EUKARYOTIC CELL 2011; 10:832-41. [PMID: 21357477 DOI: 10.1128/ec.00235-10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The role of Mid1, a stretch-activated ion channel capable of being permeated by calcium, in ascospore development and forcible discharge from asci was examined in the pathogenic fungus Gibberella zeae (anamorph Fusarium graminearum). The Δmid1 mutants exhibited a >12-fold reduction in ascospore discharge activity and produced predominately abnormal two-celled ascospores with constricted and fragile septae. The vegetative growth rate of the mutants was ∼50% of the wild-type rate, and production of macroconidia was >10-fold lower than in the wild type. To better understand the role of calcium flux, Δmid1 Δcch1 double mutants were also examined, as Cch1, an L-type calcium ion channel, is associated with Mid1 in Saccharomyces cerevisiae. The phenotype of the Δmid1 Δcch1 double mutants was similar to but more severe than the phenotype of the Δmid1 mutants for all categories. Potential and current-voltage measurements were taken in the vegetative hyphae of the Δmid1 and Δcch1 mutants and the wild type, and the measurements for all three strains were remarkably similar, indicating that neither protein contributes significantly to the overall electrical properties of the plasma membrane. Pathogenicity of the Δmid1 and Δmid1Δcch1 mutants on the host (wheat) was not affected by the mutations. Exogenous calcium supplementation partially restored the ascospore discharge and vegetative growth defects for all mutants, but abnormal ascospores were still produced. These results extend the known roles of Mid1 to ascospore development and forcible discharge. However, Neurospora crassa Δmid1 mutants were also examined and did not exhibit defects in ascospore development or in ascospore discharge. In comparison to ion channels in other ascomycetes, Mid1 shows remarkable adaptability of roles, particularly with regard to niche-specific adaptation.
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70
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Heuck S, Gerstmann UC, Michalke B, Kanter U. Genome-wide analysis of caesium and strontium accumulation in Saccharomyces cerevisiae. Yeast 2011; 27:817-35. [PMID: 20641020 DOI: 10.1002/yea.1780] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
(137)Cs and (90)Sr contribute to significant and long-lasting contamination of the environment with radionuclides. Due to their relatively high biological availability, they are transferred rapidly into biotic systems and may enter the food chain. In this study, we analysed 4862 haploid yeast knockout strains of Saccharomyces cerevisiae to identify genes involved in caesium (Cs(+)) and/or strontium (Sr(2+)) accumulation. According to this analysis, 212 mutant strains were associated with reproducible altered Cs(+) and/or Sr(2+) accumulation. These mutants were deficient for a wide range of cellular processes. Among those, the vacuolar function and biogenesis turned out to be crucial for both Cs(+) and Sr(2+) accumulation. Disruption of the vacuole diminished Cs(+) accumulation, whereas Sr(2+) enrichment was enhanced. Further analysis with a subset of the identified candidates were undertaken comparing the accumulation of Cs(+) and Sr(2+) with their essential counterparts potassium (K(+)) and calcium (Ca(2+)). Sr(2+) and Ca(2+) accumulation was highly correlated in yeast excluding the possibility of a differential regulation or uptake mechanisms. In direct contrast, the respective results suggest that Cs(+) uptake is at least partially dependent on mechanisms distinct from K(+) uptake. Single candidates (e.g. KHA1) are presented which might be specifically responsible for Cs(+) homeostasis.
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Affiliation(s)
- Sabine Heuck
- Helmholtz Zentrum München, Institut für Strahlenschutz, Neuherberg, Germany
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71
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Ethanol induces calcium influx via the Cch1-Mid1 transporter in Saccharomyces cerevisiae. Arch Microbiol 2011; 193:323-34. [PMID: 21259000 DOI: 10.1007/s00203-010-0673-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 12/02/2010] [Accepted: 12/24/2010] [Indexed: 10/18/2022]
Abstract
Yeast suffers from a variety of environmental stresses, such as osmotic pressure and ethanol produced during fermentation. Since calcium ions are protective for high concentrations of ethanol, we investigated whether Ca(2+) flux occurs in response to ethanol stress. We find that exposure of yeast to ethanol induces a rise in the cytoplasmic concentration of Ca(2+). The response is enhanced in cells shifted to high-osmotic media containing proline, galactose, sorbitol, or mannitol. Suspension of cells in proline and galactose-containing media increases the Ca(2+) levels in the cytoplasm independent of ethanol exposure. The enhanced ability for ethanol to induce Ca(2+) flux after the hypertonic shift is transient, decreasing rapidly over a period of seconds to minutes. There is partial recovery of the response after zymolyase treatment, suggesting that cell wall integrity affects the ethanol-induced Ca(2+) flux. Acetate inhibits the Ca(2+) accumulation elicited by the ethanol/osmotic stress. The Ca(2+) flux is primarily via the Cch1 Ca(2+) influx channel because strains carrying deletions of the cch1 and mid1 genes show greater than 90% reduction in Ca(2+) flux. Furthermore, a functional Cch1 channel reduced growth inhibition by ethanol.
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72
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Martin DC, Kim H, Mackin NA, Maldonado-Báez L, Evangelista CC, Beaudry VG, Dudgeon DD, Naiman DQ, Erdman SE, Cunningham KW. New regulators of a high affinity Ca2+ influx system revealed through a genome-wide screen in yeast. J Biol Chem 2011; 286:10744-54. [PMID: 21252230 DOI: 10.1074/jbc.m110.177451] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bakers' yeast Saccharomyces cerevisiae utilizes a high affinity Ca(2+) influx system (HACS) to survive assaults by mating pheromones, tunicamycin, and azole-class antifungal agents. HACS consists of two known subunits, Cch1 and Mid1, that are homologous and analogous to the catalytic α-subunits and regulatory α2δ-subunits of mammalian voltage-gated calcium channels, respectively. To search for additional subunits and regulators of HACS, a collection of gene knock-out mutants was screened for abnormal uptake of Ca(2+) after exposure to mating pheromone or to tunicamycin. The screen revealed that Ecm7 is required for HACS function in most conditions. Cycloheximide chase experiments showed that Ecm7 was stabilized by Mid1, and Mid1 was stabilized by Cch1 in non-signaling conditions, suggesting they all interact. Ecm7 is a member of the PMP-22/EMP/MP20/Claudin superfamily of transmembrane proteins that includes γ-subunits of voltage-gated calcium channels. Eleven additional members of this superfamily were identified in yeast, but none was required for HACS activity in response to the stimuli. Remarkably, many dozens of genes involved in vesicle-mediated trafficking and protein secretion were required to prevent spontaneous activation of HACS. Taken together, the findings suggest that HACS and calcineurin monitor performance of the membrane trafficking system in yeasts and coordinate compensatory processes. Conservation of this quality control system in Candida glabrata suggests that many pathogenic species of fungi may utilize HACS and calcineurin to resist azoles and other compounds that target membrane biosynthesis.
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Affiliation(s)
- D Christian Martin
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA
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73
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Verret F, Wheeler G, Taylor AR, Farnham G, Brownlee C. Calcium channels in photosynthetic eukaryotes: implications for evolution of calcium-based signalling. THE NEW PHYTOLOGIST 2010; 187:23-43. [PMID: 20456068 DOI: 10.1111/j.1469-8137.2010.03271.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Much of our current knowledge on the mechanisms by which Ca(2+) signals are generated in photosynthetic eukaryotes comes from studies of a relatively small number of model species, particularly green plants and algae, revealing some common features and notable differences between 'plant' and 'animal' systems. Physiological studies from a broad range of algal cell types have revealed the occurrence of animal-like signalling properties, including fast action potentials and fast propagating cytosolic Ca(2+) waves. Genomic studies are beginning to reveal the widespread occurrence of conserved channel types likely to be involved in Ca(2+) signalling. However, certain widespread 'ancient' channel types appear to have been lost by certain groups, such as the embryophytes. More recent channel gene loss is also evident from comparisons of more closely related algal species. The underlying processes that have given rise to the current distributions of Ca(2+) channel types include widespread retention of ancient Ca(2+) channel genes, horizontal gene transfer (including symbiotic gene transfer and acquisition of bacterial genes), gene loss and gene expansion within taxa. The assessment of the roles of Ca(2+) channel genes in diverse physiological, developmental and life history processes represents a major challenge for future studies.
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Affiliation(s)
- Frédéric Verret
- Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
| | - Glen Wheeler
- Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK
| | - Alison R Taylor
- Department of Biology and Marine Biology, University of North Carolina, 601 S. College Road, Wilmington, NC 28403, USA
| | - Garry Farnham
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK
| | - Colin Brownlee
- Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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74
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Hong MP, Vu K, Bautos J, Gelli A. Cch1 restores intracellular Ca2+ in fungal cells during endoplasmic reticulum stress. J Biol Chem 2010; 285:10951-8. [PMID: 20123986 DOI: 10.1074/jbc.m109.056218] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pathogens endure and proliferate during infection by exquisitely coping with the many stresses imposed by the host to prevent pathogen survival. Recent evidence has shown that fungal pathogens and yeast respond to insults to the endoplasmic reticulum (ER) by initiating Ca(2+) influx across their plasma membrane. Although the high affinity Ca(2+) channel, Cch1, and its subunit Mid1, have been suggested as the protein complex responsible for mediating Ca(2+) influx, a direct demonstration of the gating mechanism of the Cch1 channel remains elusive. In this first mechanistic study of Cch1 channel activity we show that the Cch1 channel from the model human fungal pathogen, Cryptococcus neoformans, is directly activated by the depletion of intracellular Ca(2+) stores. Electrophysiological analysis revealed that agents that enable ER Ca(2+) store depletion promote the development of whole cell inward Ca(2+) currents through Cch1 that are effectively blocked by La(3+) and dependent on the presence of Mid1. Cch1 is permeable to both Ca(2+) and Ba(2+); however, unexpectedly, in contrast to Ca(2+) currents, Ba(2+) currents are steeply voltage-dependent. Cch1 maintains a strong Ca(2+) selectivity even in the presence of high concentrations of monovalent ions. Single channel analysis indicated that Cch1 channel conductance is small, similar to that reported for the Ca(2+) current I(CRAC). This study demonstrates that Cch1 functions as a store-operated Ca(2+)-selective channel that is gated by intracellular Ca(2+) depletion. The inability of cryptococcal cells that lacked the Cch1-Mid1 channel to survive ER stress suggests that Cch1 and its co-regulator, Mid1, are critical players in the restoration of Ca(2+) homeostasis.
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Affiliation(s)
- Min-Pyo Hong
- Department of Pharmacology, School of Medicine, University of California, Davis, California 95616, USA
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75
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Abstract
Cellular electrophysiological systems, like developmental systems, appear to evolve primarily by means of regulatory evolution. It is suggested that electrophysiological systems share two key features with developmental systems that account for this dependence on regulatory evolution. For both systems, structural evolution has the potential to create significant problems of pleiotropy and both systems are predominantly computational in nature. It is concluded that the relative balance of physical and computational tasks that a biological system has to perform, combined with the probability that these tasks may have to change significantly during the course of evolution, will be major factors in determining the relative mix of regulatory and structural evolution that is observed for a given system. Physiological systems that directly interface with the environment will almost always perform some low-level physical task. In the majority of cases this will require evolution of protein function in order for the tasks themselves to evolve. For complex physiological systems a large fraction of their function will be devoted to high-level control functions that are predominantly computational in nature. In most cases regulatory evolution will be sufficient in order for these computational tasks to evolve.
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Affiliation(s)
- Barbara Rosati
- Department of Physiology and Biophysics, Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY 11794, USA
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76
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Deletion of Mid1, a putative stretch-activated calcium channel in Claviceps purpurea, affects vegetative growth, cell wall synthesis and virulence. Microbiology (Reading) 2009; 155:3922-3933. [DOI: 10.1099/mic.0.030825-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The putative Claviceps purpurea homologue of the Saccharomyces cerevisiae stretch-activated calcium ion channel Mid1 was investigated for its role in vegetative growth, differentiation and pathogenicity on rye (Secale cereale). Gene replacement mutants of Cl. purpurea mid1 were not affected in polar growth and branching in axenic culture but showed a significantly reduced growth rate. The growth defect could not be complemented by Ca2+ supplementation, in contrast to mid1 mutants in yeast, but the altered sensitivity of the mutants to changes in external and internal Ca2+ concentrations indicates some role of Mid1 in Ca2+ homeostasis. The major effect of mid1 deletion, however, was the complete loss of virulence: infected rye plants showed no disease symptoms at all. Detailed analyses of in vitro-infected rye ovaries demonstrated that the Δmid1 mutants had multiple apical branches and were unable to infect the host tissue, suggesting that Mid1 is essential for generating the necessary mechanical force for penetration. This is believed to be the first report of an essential role for a Mid1 homologue in the virulence of a plant-pathogenic fungus.
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77
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Courchesne WE, Tunc M, Liao S. Amiodarone induces stress responses and calcium flux mediated by the cell wall in Saccharomyces cerevisiae. Can J Microbiol 2009; 55:288-303. [PMID: 19370072 DOI: 10.1139/w08-132] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used a proteomic approach to study effects of amiodarone on cells of the yeast Saccharomyces cerevisiae. Amiodarone has been shown to have antifungal activity in vitro and causes a massive increase in cytoplasmic calcium levels ([Ca2+]cyt). Proteomic analysis of cells exposed to amiodarone show that this drug elicits stress responses and points to involvement of proteins associated with the cell wall. We tested several of those proteins for involvement in the Ca2+ flux. In particular, the amiodarone-induced Ca2+ flux was decreased in bgl2Delta cells, which have altered levels of beta-glucan and chitin. The involvement of the cell wall in the Ca2+ flux induced by amiodarone treatment was tested by addition of yeast cell-wall components. While mannan inhibited the rise in [Ca2+]cyt, beta-glucan potentiated the Ca2+ flux by 4.5-fold, providing evidence that the cell wall is directly involved in controlling this Ca2+ flux. This conclusion is corroborated by the inhibition of the Ca2+ flux by calcofluor, which is known to bind to cell-wall chitin and inhibit cell growth. Zymolyase treatment altered the kinetics of amiodarone-induced calcium flux and uncoupled the inhibitory effect of calcofluor. These effects demonstrate that the cell-wall beta-glucan regulates calcium flux elicited by amiodarone.
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Affiliation(s)
- William E Courchesne
- Department of Microbiology and Immunology, School of Medicine, University of Nevada, Reno, NV 89557, USA.
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78
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Clemente-Ramos JA, Martín-García R, Sharifmoghadam MR, Konomi M, Osumi M, Valdivieso MH. The tetraspan protein Dni1p is required for correct membrane organization and cell wall remodelling during mating in Schizosaccharomyces pombe. Mol Microbiol 2009; 73:695-709. [PMID: 19627505 DOI: 10.1111/j.1365-2958.2009.06800.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In fungi, success of mating requires that both cells agglutinate, modify their extracellular envelopes, and fuse their plasma membranes and nuclei to produce a zygote. Here we studied the role of the Schizosaccharomyces pombe Dni1 protein in the cell fusion step of mating. Dni1p is a tetraspan protein bearing a conserved cystein motif similar to that present in fungal claudin-related proteins. Dni1p expression is induced during mating and Dni1p concentrates as discrete patches at the cell-cell contact area and along the mating bridge. Proper Dni1p localization depends on Fus1p, actin and integrity of lipid rafts. In dni1Delta mutants, cell differentiation and agglutination are as efficient as in the wild-type strain, but cell fusion is significantly reduced at temperatures above 25 degrees C. We found that the defect in cell fusion was not associated with an altered cytoskeleton, with an abnormal distribution of Fus1p, or with a defect in calcium accumulation, but with a severe disorganization of the plasma membrane and cell wall at the area of cell-cell contact. These results show that Dni1p plays a relevant role in co-ordinating membrane organization and cell wall remodelling during mating, a function that has not been described for other proteins in the fission yeast.
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Affiliation(s)
- José Angel Clemente-Ramos
- Departamento de Microbiología y Genética/Instituto de Microbiología Bioquímica, Universidad de Salamanca/CSIC, Edificio Departamental, 37007-Salamanca, Spain
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79
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The functional expression of toxic genes: lessons learned from molecular cloning of CCH1, a high-affinity Ca2+ channel. Anal Biochem 2009; 393:234-41. [PMID: 19580778 DOI: 10.1016/j.ab.2009.06.039] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2009] [Revised: 06/28/2009] [Accepted: 06/30/2009] [Indexed: 11/22/2022]
Abstract
Some genes cannot be cloned by conventional methods because in most cases the genes or gene products are toxic to Escherichia coli. CCH1 is a high-affinity Ca(2+) channel present in the plasma membrane of Cryptococcus neoformans and other fungi. Like many toxic genes, the molecular cloning of CCH1 has been a major challenge; consequently, direct studies of CCH1 channel activity in heterologous expression systems have been impossible. We have devised a straightforward approach that resulted in the molecular cloning and functional expression of CCH1 by exploiting homologous recombination both in vitro and in vivo. This approach precluded the standard enzyme digestion-mediated ligation reactions and the subsequent isolation of plasmids from E. coli. The shuttle plasmid carrying CCH1-GFP, which was prepared in vitro and propagated in yeast, was successfully expressed in the mammalian cell line HEK293 (human embryonic kidney 293). CCH1 transcripts were detected only in HEK293 cells transfected with the plasmid DNA. Fluorescence microscopy studies revealed the expression of CCH1-GFP fusion protein on the cell surface of HEK293 cells, similar to the localization pattern of a well-characterized plasma membrane-associated K(+) channel. This approach will be particularly useful for genes that encode ion channels and transporters that cannot be cloned by conventional techniques requiring E. coli.
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80
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Teng J, Goto R, Iida K, Kojima I, Iida H. Ion-channel blocker sensitivity of voltage-gated calcium-channel homologue Cch1 in Saccharomyces cerevisiae. Microbiology (Reading) 2008; 154:3775-3781. [DOI: 10.1099/mic.0.2008/021089-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Jinfeng Teng
- Laboratory of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8510, Japan
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
| | - Rika Goto
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
| | - Kazuko Iida
- Biomembrane Signaling Project 2, Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan
| | - Itaru Kojima
- Laboratory of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8510, Japan
| | - Hidetoshi Iida
- Department of Bioenvironmental Science, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki, Aichi 444-8787, Japan
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
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81
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Abstract
Studies of ion channels have for long been dominated by the animalcentric, if not anthropocentric, view of physiology. The structures and activities of ion channels had, however, evolved long before the appearance of complex multicellular organisms on earth. The diversity of ion channels existing in cellular membranes of prokaryotes is a good example. Although at first it may appear as a paradox that most of what we know about the structure of eukaryotic ion channels is based on the structure of bacterial channels, this should not be surprising given the evolutionary relatedness of all living organisms and suitability of microbial cells for structural studies of biological macromolecules in a laboratory environment. Genome sequences of the human as well as various microbial, plant, and animal organisms unambiguously established the evolutionary links, whereas crystallographic studies of the structures of major types of ion channels published over the last decade clearly demonstrated the advantage of using microbes as experimental organisms. The purpose of this review is not only to provide an account of acquired knowledge on microbial ion channels but also to show that the study of microbes and their ion channels may also hold a key to solving unresolved molecular mysteries in the future.
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Affiliation(s)
- Boris Martinac
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia.
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82
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Evidence for the role of calcineurin in morphogenesis and calcium homeostasis during mycelium-to-yeast dimorphism of Paracoccidioides brasiliensis. EUKARYOTIC CELL 2008; 7:1856-64. [PMID: 18776037 DOI: 10.1128/ec.00110-08] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Paracoccidioides brasiliensis is a dimorphic fungus that causes paracoccidioidomycosis, the most prevalent human deep mycosis in Latin America. The dimorphic transition from mycelium to yeast (M-Y) is triggered by a temperature shift from 25 degrees C to 37 degrees C and is critical for pathogenicity. Intracellular Ca(2+) levels increased in hyphae immediately after temperature-induced dimorphism. The chelation of Ca(2+) with extracellular (EGTA) or intracellular (BAPTA) calcium chelators inhibited temperature-induced dimorphism, whereas the addition of extracellular Ca(2+) accelerated dimorphism. The calcineurin inhibitor cyclosporine A (CsA), but not tacrolimus (FK506), effectively decreased cell growth, halted the M-Y transition that is associated with virulence, and caused aberrant growth morphologies for all forms of P. brasiliensis. The difference between CsA and FK506 was ascribed by the higher levels of cyclophilins contrasted to FKBPs, the intracellular drug targets required for calcineurin suppression. Chronic exposure to CsA abolished intracellular Ca(2+) homeostasis and decreased mRNA transcription of the CCH1 gene for the plasma membrane Ca(2+) channel in yeast-form cells. CsA had no detectable effect on multidrug resistance efflux pumps, while the effect of FK506 on rhodamine excretion was not correlated with the transition to yeast form. In this study, we present evidence that Ca(2+)/calmodulin-dependent phosphatase calcineurin controls hyphal and yeast morphology, M-Y dimorphism, growth, and Ca(2+) homeostasis in P. brasiliensis and that CsA is an effective chemical block for thermodimorphism in this organism. The effects of calcineurin inhibitors on P. brasiliensis reinforce the therapeutic potential of these drugs in a combinatory approach with antifungal drugs to treat endemic paracoccidioidomycosis.
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83
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Lew RR, Abbas Z, Anderca MI, Free SJ. Phenotype of a mechanosensitive channel mutant, mid-1, in a filamentous fungus, Neurospora crassa. EUKARYOTIC CELL 2008; 7:647-55. [PMID: 18296620 PMCID: PMC2292622 DOI: 10.1128/ec.00411-07] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 02/12/2008] [Indexed: 12/21/2022]
Abstract
In the yeast Saccharomyces cerevisiae, the MID1 (mating-induced death) gene encodes a stretch-activated channel which is required for successful mating; the mutant phenotype is rescued by elevated extracellular calcium. Homologs of the MID1 gene are found in fungi that are morphologically complex compared to yeast, both Basidiomycetes and Ascomycetes. We explored the phenotype of a mid-1 knockout mutant in the filamentous ascomycete Neurospora crassa. The mutant exhibits lower growth vigor than the wild type (which is not rescued by replete calcium) and mates successfully. Thus, the role of the MID-1 protein differs from that of the homologous gene product in yeast. Hyphal cytology, growth on diverse carbon sources, turgor regulation, and circadian rhythms of the mid-1 mutant are all similar to those of the wild type. However, basal turgor is lower than wild type, as is the activity of the plasma membrane H(+)-ATPase (measured by cyanide [CN(-)]-induced depolarization of the energy-dependent component of the membrane potential). In addition, the mutant is unable to grow at low extracellular Ca(2+) levels or when cytoplasmic Ca(2+) is elevated with the Ca(2+) ionophore A23187. We conclude that the MID-1 protein plays a role in regulation of ion transport via Ca(2+) homeostasis and signaling. In the absence of normal ion transport activity, the mutant exhibits poorer growth.
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Affiliation(s)
- Roger R Lew
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
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84
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Cdc1p is an endoplasmic reticulum-localized putative lipid phosphatase that affects Golgi inheritance and actin polarization by activating Ca2+ signaling. Mol Cell Biol 2008; 28:3336-43. [PMID: 18332110 DOI: 10.1128/mcb.00567-07] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the budding yeast Saccharomyces cerevisiae, mutations in the essential gene CDC1 cause defects in Golgi inheritance and actin polarization. However, the biochemical function of Cdc1p is unknown. Previous work showed that cdc1 mutants accumulate intracellular Ca(2+) and display enhanced sensitivity to the extracellular Mn(2+) concentration, suggesting that Cdc1p might regulate divalent cation homeostasis. By contrast, our data indicate that Cdc1p is a Mn(2+)-dependent protein that can affect Ca(2+) levels. We identified a cdc1 allele that activates Ca(2+) signaling but does not show enhanced sensitivity to the Mn(2+) concentration. Furthermore, our studies show that Cdc1p is an endoplasmic reticulum-localized transmembrane protein with a putative phosphoesterase domain facing the lumen. cdc1 mutant cells accumulate an unidentified phospholipid, suggesting that Cdc1p may be a lipid phosphatase. Previous work showed that deletion of the plasma membrane Ca(2+) channel Cch1p partially suppressed the cdc1 growth phenotype, and we find that deletion of Cch1p also suppresses the Golgi inheritance and actin polarization phenotypes. The combined data fit a model in which the cdc1 mutant phenotypes result from accumulation of a phosphorylated lipid that activates Ca(2+) signaling.
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85
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Rodriguez-Franco M, Sarmiento F, Marquardt K, Markus R, Neuhaus G. Does light taste salty? PLANT SIGNALING & BEHAVIOR 2008; 3:72-3. [PMID: 19704777 PMCID: PMC2633967 DOI: 10.4161/psb.3.1.4925] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 08/23/2007] [Indexed: 05/21/2023]
Abstract
As research advances acquisition of new data reveals novel aspects on already investigated issues. This is the case for SALT TOLERANCE (STO), an Arabidopsis protein that confers tolerance to high salt concentrations when ectopically expressed in yeast cells. For the last years, STO was considered to participate mainly in the response and tolerance of Arabidopsis to high salinity, as it does in yeast. However, recent investigations using gain- and loss-of-function mutants revealed a major role for STO as negative regulator of photomorphogenesis. Interestingly, and contrary to other negative regulators of light dependent inhibition of hypocotyl elongation, STO protein instability is controlled by COP1 activity in etiolated seedlings. Thus, light stabilizes STO protein levels during de-etiolation. Whether STO participates in other signaling cascades different from light signaling, as it has been shown in yeast and proposed in plants or not, is still an open question.
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86
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Kullas AL, Martin SJ, Davis D. Adaptation to environmental pH: integrating the Rim101 and calcineurin signal transduction pathways. Mol Microbiol 2007; 66:858-71. [PMID: 17927701 DOI: 10.1111/j.1365-2958.2007.05929.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The ability to appropriately respond to environmental conditions is critical for the survival of simple microbes and for development of complex multicellular organisms. Sensing and responding to a given environmental condition requires the integration of numerous signals through one or more signal transduction pathways. This leads to changes in gene expression, and potentially post-translational modifications, that favour growth in the given environment. In the fungus Candida albicans, an important opportunistic pathogen, environmental pH has profound effects on morphology and proper adaptation to extracellular pH is critical for pathogenesis. Here, we demonstrate that the Rim101/PacC pH-sensing pathway acts in parallel to Crz1, via calcineurin, to adapt to alkaline pH. We also show that the Rim101 pathway acts in parallel to Crz2, independent of calcineurin, to adapt to high lithium concentrations and to repress filamentation at acidic pH. Our studies also revealed a novel requirement for Crz1, Crz2 and calcineurin for growth at acidic pH. From these studies, we propose that the Crz1 homologue Crz2 is calcineurin-independent, but like Crz1, acts in parallel to promote specific Rim101-dependent processes. These results establish and begin to dissect the complex interactions between important signal transduction pathways in C. albicans, which are critical for virulence.
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Affiliation(s)
- Amy L Kullas
- Department of Microbiology, University of Minnesota, Minneapolis, MN 55455, USA
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87
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Bieszke JA, Li L, Borkovich KA. The fungal opsin gene nop-1 is negatively-regulated by a component of the blue light sensing pathway and influences conidiation-specific gene expression in Neurospora crassa. Curr Genet 2007; 52:149-57. [PMID: 17676324 DOI: 10.1007/s00294-007-0148-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 07/17/2007] [Accepted: 07/18/2007] [Indexed: 10/23/2022]
Abstract
We previously demonstrated that the nop-1 gene encodes a putative green-light opsin photoreceptor that is highly expressed in cultures that support asexual sporulation (conidiation) in Neurospora crassa. In this study, we demonstrate that nop-1 is a late-stage conidiation gene, through analysis of nop-1 transcript levels in wild-type strains and mutants blocked at various stages of conidiation. nop-1 message amounts are similar with constant illumination or darkness during conidiation, consistent with developmental, but not light, regulation of nop-1 expression. Furthermore, photoinduction experiments using wild type and mutants defective in components of the blue light sensing pathway (wc-1 and wc-2) indicate that nop-1 mRNA levels are not appreciably affected by brief light exposure during conidiation. Surprisingly, nop-1 message amounts are greatly elevated in wc-2 mutants in light or dark, suggesting that the wc-2 gene product regulates nop-1 expression in a light-independent manner. Analysis of expression patterns for al-2, con-10 and con-13, genes regulated by conidiation and/or blue light, showed that nop-1 has significant and reproducible effects on all three genes during various stages of conidiation. The results suggest that NOP-1 directly or indirectly modulates carotenogenesis and repression of conidiation-specific gene expression in N. crassa.
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Affiliation(s)
- Jennifer A Bieszke
- Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School, 6431 Fannin Street, JFB 1.765, Houston, TX 77030, USA
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88
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Indorf M, Cordero J, Neuhaus G, Rodríguez-Franco M. Salt tolerance (STO), a stress-related protein, has a major role in light signalling. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 51:563-74. [PMID: 17605755 DOI: 10.1111/j.1365-313x.2007.03162.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The salt tolerance protein (STO) of Arabidopsis was identified as a protein conferring salt tolerance to yeast cells. In order to uncover its function, we isolated an STO T-DNA insertion line and generated RNAi and overexpressor Arabidopsis plants. Here we present data on the hypocotyl growth of these lines indicating that STO acts as a negative regulator in phytochrome and blue-light signalling. Transcription analysis of STO uncovered a light and circadian dependent regulation of gene expression, and analysis of light-regulated genes revealed that STO is involved in the regulation of CHS expression during de-etiolation. In addition, we could show that CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) represses the transcription of STO and contributes to the destabilization of the protein in etiolated seedlings. Microscopic analysis revealed that the STO:eGFP fusion protein is located in the nucleus, accumulates in a light-dependent manner, and, in transient transformation assays in onion epidermal cells, co-localizes with COP1 in nuclear and cytoplasmic aggregations. However, the analysis of gain- and loss-of-function STO mutants in the cop1-4 background points towards a COP1-independent role during photomorphogenesis.
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Affiliation(s)
- Martin Indorf
- Department of Cell Biology, University of Freiburg, Freiburg D-79104, Germany
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89
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Iida K, Teng J, Tada T, Saka A, Tamai M, Izumi-Nakaseko H, Adachi-Akahane S, Iida H. Essential, completely conserved glycine residue in the domain III S2-S3 linker of voltage-gated calcium channel alpha1 subunits in yeast and mammals. J Biol Chem 2007; 282:25659-67. [PMID: 17569661 DOI: 10.1074/jbc.m703757200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated Ca2+ channels (VGCCs) mediate the influx of Ca2+ that regulates many cellular events, and mutations in VGCC genes cause serious hereditary diseases in mammals. The yeast Saccharomyces cerevisiae has only one gene encoding the putative pore-forming alpha1 subunit of VGCC, CCH1. Here, we identify a cch1 allele producing a completely nonfunctional Cch1 protein with a Gly1265 to Glu substitution present in the domain III S2-S3 cytoplasmic linker. Comparison of amino acid sequences of this linker among 58 VGCC alpha1 subunits from 17 species reveals that a Gly residue whose position corresponds to that of the Cch1 Gly1265 is completely conserved from yeasts to humans. Systematic amino acid substitution analysis using 10 amino acids with different chemical and structural properties indicates that the Gly1265 is essential for Cch1 function because of the smallest residue volume. Replacement of the Gly959 residue of a rat brain Cav1.2 alpha1 subunit (rbCII), positionally corresponding to the yeast Cch1 Gly1265, with Glu, Ser, Lys, or Ala results in the loss of Ba2+ currents, as revealed by the patch clamp method. These results suggest that the Gly residue in the domain III S2-S3 linker is functionally indispensable from yeasts to mammals. Because the Gly residue has never been studied in any VGCC, these findings provide new insights into the structure-function relationships of VGCCs.
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Affiliation(s)
- Kazuko Iida
- Biomembrane Signaling Project 2, Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan
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90
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Wolfe DM, Pearce DA. Channeling studies in yeast: yeast as a model for channelopathies? Neuromolecular Med 2007; 8:279-306. [PMID: 16775381 DOI: 10.1385/nmm:8:3:279] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Revised: 11/30/1999] [Accepted: 01/09/2006] [Indexed: 01/30/2023]
Abstract
Regulation of the concentration of ions within a cell is mediated by their specific transport and sequestration across cellular membranes. This regulation constitutes a major factor in the maintenance of correct cellular homeostasis, with the transport occurring through the action of a large number of different channel proteins localized to the plasma membrane as well as to various organelles. These ion channels vary in specificity from broad (cationic vs anionic) to highly selective (chloride vs sodium). Mutations in many of these channels result in a large number of human diseases, collectively termed channelopathies. Characterization of many of these channels has been undertaken in a variety of both prokaryotic and eukaryotic organisms. Among these organisms is the budding yeast Saccharomyces cerevisiae. Possessing a fully annotated genome, S. cerevisiae would appear to be an ideal organism in which to study this class of proteins associated to diseases. We have compiled and reviewed a list of yeast ion channels, each possessing a human homolog implicated in a channelopathy. Although yeast has been used for the study of other human disease, it has been under utilized for channelopathy research. The utility of using yeast as a model system for studying ion channels associated to human disease is illustrated using yeast lacking the GEF1 gene product that encodes the human homolog to the chloride channel CLC-3.
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Affiliation(s)
- Devin M Wolfe
- Center for Aging and Developmental Biology, Aab Institute of Biomedical Sciences, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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91
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Jung WH, Sham A, White R, Kronstad JW. Iron regulation of the major virulence factors in the AIDS-associated pathogen Cryptococcus neoformans. PLoS Biol 2007; 4:e410. [PMID: 17121456 PMCID: PMC1637126 DOI: 10.1371/journal.pbio.0040410] [Citation(s) in RCA: 176] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 09/22/2006] [Indexed: 11/18/2022] Open
Abstract
Iron overload is known to exacerbate many infectious diseases, and conversely, iron withholding is an important defense strategy for mammalian hosts. Iron is a critical cue for Cryptococcus neoformans because the fungus senses iron to regulate elaboration of the polysaccharide capsule that is the major virulence factor during infection. Excess iron exacerbates experimental cryptococcosis and the prevalence of this disease in Sub-Saharan Africa has been associated with nutritional and genetic aspects of iron loading in the background of the HIV/AIDS epidemic. We demonstrate that the iron-responsive transcription factor Cir1 in Cr. neoformans controls the regulon of genes for iron acquisition such that cir1 mutants are "blind" to changes in external iron levels. Cir1 also controls the known major virulence factors of the pathogen including the capsule, the formation of the anti-oxidant melanin in the cell wall, and the ability to grow at host body temperature. Thus, the fungus is remarkably tuned to perceive iron as part of the disease process, as confirmed by the avirulence of the cir1 mutant; this characteristic of the pathogen may provide opportunities for antifungal treatment.
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Affiliation(s)
- Won Hee Jung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Anita Sham
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rick White
- Department of Statistics, University of British Columbia, Vancouver, British Columbia, Canada
| | - James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
- * To whom correspondence should be addressed. E-mail:
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92
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Nakagawa Y, Katagiri T, Shinozaki K, Qi Z, Tatsumi H, Furuichi T, Kishigami A, Sokabe M, Kojima I, Sato S, Kato T, Tabata S, Iida K, Terashima A, Nakano M, Ikeda M, Yamanaka T, Iida H. Arabidopsis plasma membrane protein crucial for Ca2+ influx and touch sensing in roots. Proc Natl Acad Sci U S A 2007; 104:3639-44. [PMID: 17360695 PMCID: PMC1802001 DOI: 10.1073/pnas.0607703104] [Citation(s) in RCA: 279] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2006] [Indexed: 11/18/2022] Open
Abstract
Plants can sense and respond to mechanical stimuli, like animals. An early mechanism of mechanosensing and response is speculated to be governed by as-yet-unidentified sensory complexes containing a Ca(2+)-permeable, stretch-activated (SA) channel. However, the components or regulators of such complexes are poorly understood at the molecular level in plants. Here, we report the molecular identification of a plasma membrane protein (designated Mca1) that correlates Ca(2+) influx with mechanosensing in Arabidopsis thaliana. MCA1 cDNA was cloned by the functional complementation of lethality of a yeast mid1 mutant lacking a putative Ca(2+)-permeable SA channel component. Mca1 was localized to the yeast plasma membrane as an integral membrane protein and mediated Ca(2+) influx. Mca1 also increased [Ca(2+)](cyt) upon plasma membrane distortion in Arabidopsis. The growth of MCA1-overexpressing plants was impaired in a high-calcium but not a low-calcium medium. The primary roots of mca1-null plants failed to penetrate a harder agar medium from a softer one. These observations demonstrate that Mca1 plays a crucial role in a Ca(2+)-permeable SA channel system that leads to mechanosensing in Arabidopsis. We anticipate our findings to be a starting point for a deeper understanding of the molecular mechanisms of mechanotransduction in plants.
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Affiliation(s)
- Yuko Nakagawa
- Department of Biology, Tokyo Gakugei University, Tokyo 184-8501, Japan
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93
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Brand A, Shanks S, Duncan VM, Yang M, Mackenzie K, Gow NA. Hyphal orientation of Candida albicans is regulated by a calcium-dependent mechanism. Curr Biol 2007; 17:347-52. [PMID: 17275302 PMCID: PMC1885950 DOI: 10.1016/j.cub.2006.12.043] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 12/08/2006] [Accepted: 12/12/2006] [Indexed: 01/14/2023]
Abstract
Eukaryotic cells from fungal hyphae to neurites that grow by polarized extension must coordinate cell growth and cell orientation to enable them to exhibit growth tropisms and to respond to relevant environmental cues. Such cells generally maintain a tip-high Ca2+ cytoplasmic gradient, which is correlated with their ability to exhibit polarized tip growth and to respond to growth-directing extracellular signals 1, 2, 3, 4, 5. In yeast and other fungi, the polarisome, exocyst, Arp2/3, and Spitzenkörper protein complexes collectively orchestrate tip growth and cell polarity, but it is not clear whether these molecular complexes also regulate cell orientation or whether they are influenced by cytoplasmic Ca2+ gradients. Hyphae of the human pathogenic fungus Candida albicans reorient their growth axis in response to underlying surface topography (thigmotropism) [6] and imposed electric fields (galvanotropism) [7]. The establishment and maintenance of directional growth in relation to these environmental cues was Ca2+ dependent. Tropisms were attenuated in media containing low Ca2+, or calcium-channel blockers, and in mutants where calcium channels or elements of the calcium signaling pathway were deleted. Therefore galvanotropism and thigmotropism may both be mediated by localized Ca2+ influx at sites of polarized growth via Ca2+ channels that are activated by appropriate environmental signals.
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Affiliation(s)
- Alexandra Brand
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Scott Shanks
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Vanessa M.S. Duncan
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Meng Yang
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Kevin Mackenzie
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Neil A.R. Gow
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
- Corresponding author
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94
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Humphrey TV, Bonetta DT, Goring DR. Sentinels at the wall: cell wall receptors and sensors. THE NEW PHYTOLOGIST 2007; 176:7-21. [PMID: 17803638 DOI: 10.1111/j.1469-8137.2007.02192.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The emerging view of the plant cell wall is of a dynamic and responsive structure that exists as part of a continuum with the plasma membrane and cytoskeleton. This continuum must be responsive and adaptable to normal processes of growth as well as to stresses such as wounding, attack from pathogens and mechanical stimuli. Cell expansion involving wall loosening, deposition of new materials, and subsequent rigidification must be tightly regulated to allow the maintenance of cell wall integrity and co-ordination of development. Similarly, sensing and feedback are necessary for the plant to respond to mechanical stress or pathogen attack. Currently, understanding of the sensing and feedback mechanisms utilized by plants to regulate these processes is limited, although we can learn from yeast, where the signalling pathways have been more clearly defined. Plant cell walls possess a unique and complicated structure, but it is the protein components of the wall that are likely to play a crucial role at the forefront of perception, and these are likely to include a variety of sensor and receptor systems. Recent plant research has yielded a number of interesting candidates for cell wall sensors and receptors, and we are beginning to understand the role that they may play in this crucial aspect of plant biology.
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Affiliation(s)
- Tania V Humphrey
- Department of Cell and Systems Biology, University of Toronto, 25 Willcocks St, Toronto, Ontario, M5S 3B2 Canada
| | - Dario T Bonetta
- Faculty of Science, University of Ontario Institute of Technology, 2000 Simcoe St North, Science Building UA4000, Oshawa, Ontario, L1H 7K4 Canada
| | - Daphne R Goring
- Department of Cell and Systems Biology, University of Toronto, 25 Willcocks St, Toronto, Ontario, M5S 3B2 Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
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95
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Liu M, Du P, Heinrich G, Cox GM, Gelli A. Cch1 mediates calcium entry in Cryptococcus neoformans and is essential in low-calcium environments. EUKARYOTIC CELL 2006; 5:1788-96. [PMID: 16950930 PMCID: PMC1595334 DOI: 10.1128/ec.00158-06] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Accepted: 08/21/2006] [Indexed: 11/20/2022]
Abstract
The ability of Cryptococcus neoformans to grow at the mammalian body temperature (37 degrees C to 39 degrees C) is a well-established virulence factor. Growth of C. neoformans at this physiological temperature requires calcineurin, a Ca(2+)/calmodulin-dependent protein phosphatase. When cytosolic calcium concentrations are low ( approximately 50 to 100 nM), calcineurin is inactive and becomes active only when cytosolic calcium concentrations rise ( approximately 1 to 10 microM) through the activation of calcium channels. In this study we analyzed the function of Cch1 in C. neoformans and found that Cch1 is a Ca(2+)-permeable channel that mediates calcium entry in C. neoformans. Analysis of the Cch1 protein sequence revealed differences in the voltage sensor (S4 regions), suggesting that Cch1 may have diminished voltage sensitivity or possibly an alternative gating mechanism. The inability of the cch1 mutant to grow under conditions of limited extracellular calcium concentrations ([Ca(2+)](extracellular), approximately 100 nM) suggested that Cch1 was required for calcium uptake in low-calcium environments. These results are consistent with the role of ScCch1 in mediating high-affinity calcium uptake in Saccharomyces cerevisiae. Although the growth defect of the cch1 mutant under conditions of limited [Ca(2+)](extracellular) ( approximately 100 nM) became more severe with increasing temperature (25 degrees C to 38.5 degrees ), this temperature sensitivity was not observed when the cch1 mutant was grown on rich medium ([Ca(2+)](extracellular), approximately 0.140 mM). Accordingly, the cch1 mutant strain displayed only attenuated virulence when tested in the mouse inhalation model of cryptococcosis, further suggesting that C. neoformans may have a limited requirement for Cch1 and that this requirement appears to include ion stress tolerance.
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Affiliation(s)
- Min Liu
- Department of Medical Pharmacology and Toxicology, University of California, Davis, Genome and Biomedical Sciences Facility, Davis, CA 95616, USA.
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96
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Zhang NN, Dudgeon DD, Paliwal S, Levchenko A, Grote E, Cunningham KW. Multiple signaling pathways regulate yeast cell death during the response to mating pheromones. Mol Biol Cell 2006; 17:3409-22. [PMID: 16738305 PMCID: PMC1525234 DOI: 10.1091/mbc.e06-03-0177] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mating pheromones promote cellular differentiation and fusion of yeast cells with those of the opposite mating type. In the absence of a suitable partner, high concentrations of mating pheromones induced rapid cell death in approximately 25% of the population of clonal cultures independent of cell age. Rapid cell death required Fig1, a transmembrane protein homologous to PMP-22/EMP/MP20/Claudin proteins, but did not require its Ca2+ influx activity. Rapid cell death also required cell wall degradation, which was inhibited in some surviving cells by the activation of a negative feedback loop involving the MAP kinase Slt2/Mpk1. Mutants lacking Slt2/Mpk1 or its upstream regulators also underwent a second slower wave of cell death that was independent of Fig1 and dependent on much lower concentrations of pheromones. A third wave of cell death that was independent of Fig1 and Slt2/Mpk1 was observed in mutants and conditions that eliminate calcineurin signaling. All three waves of cell death appeared independent of the caspase-like protein Mca1 and lacked certain "hallmarks" of apoptosis. Though all three waves of cell death were preceded by accumulation of reactive oxygen species, mitochondrial respiration was only required for the slowest wave in calcineurin-deficient cells. These findings suggest that yeast cells can die by necrosis-like mechanisms during the response to mating pheromones if essential response pathways are lacking or if mating is attempted in the absence of a partner.
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Affiliation(s)
| | | | - Saurabh Paliwal
- Whitaker Institute for Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218; and
| | - Andre Levchenko
- Whitaker Institute for Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218; and
| | - Eric Grote
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
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97
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Karababa M, Valentino E, Pardini G, Coste AT, Bille J, Sanglard D. CRZ1, a target of the calcineurin pathway inCandida albicans. Mol Microbiol 2006; 59:1429-51. [PMID: 16468987 DOI: 10.1111/j.1365-2958.2005.05037.x] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Calcineurin is a major player in calcium-dependent signal transduction pathways of eukaryotes. Calcineurin acts on transcription factors (e.g. CRZ1 in Saccharomyces cerevisiae) and governs the expression of genes in a species-dependent fashion. In Candida albicans, the calcineurin pathway is involved in tolerance to antifungal agents, cation homeostasis and virulence. However, the components of the calcineurin pathway are still poorly investigated in this yeast species. Taking S. cerevisiae as a model to reconstitute this pathway, two CRZ1-like genes, CRZ1 and CRZ2 (for calcineurin-responsive zinc finger 1 and 2 genes), were found with C(2)H(2) zinc finger domains. Only CRZ1 was able to restore the calcium hypersusceptibility of a S. cerevisiae crz1Delta mutant and to mediate calcium-dependent gene expression in this yeast species. Several experiments showed that CRZ1 was dependent on calcineurin in C. albicans: (i) phenotypic analysis of a crz1Delta/Delta mutant showed impaired growth as compared with the wild type in the presence of cations (Ca(2+), Mn(2+)) as does a mutant lacking calcineurin subunit A (cnaDelta/Delta) and (ii) a green fluorescent protein (GFP)-Crz1p fusion protein showed a calcium- and calcineurin-dependent nuclear localization. To further analyse the relationship between calcineurin and CRZ1, a comprehensive analysis of calcineurin/Crz1p-dependent gene expression following addition of Ca(2+) (200 mM) was performed. Among the expression of 264 genes altered by at least twofold, the upregulation of 60 genes was dependent on both calcineurin and CRZ1. Interestingly, a motif [5'-G(C/T)GGT-3'] with similarity to the target sequence of Crz1p (GNGGCG/TCA) from S. cerevisiae was identified as a putative regulatory sequence in the upstream regions of these calcineurin/Crz1p-dependent genes. However, additional experiments showed that calcineurin may have other targets in addition to CRZ1. First, CRZ1 was not involved in tolerance to antifungal agents (fluconazole, terbinafine) on the opposite to calcineurin. Second, CRZ1 was only moderately influencing virulence in a mice model of infection which is in sharp contrast to the strong avirulence of cnaDelta/Delta mutant in the same animal model. Even though this work establishes CRZ1 as a calcineurin target, further studies are needed to identify other calcineurin-dependent elements in C. albicans.
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Affiliation(s)
- Mahir Karababa
- Institute of Microbiology, University Hospital Lausanne, CH-1011 Lausanne, Switzerland
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98
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Noma S, Iida K, Iida H. Polarized morphogenesis regulator Spa2 is required for the function of putative stretch-activated Ca2+-permeable channel component Mid1 in Saccharomyces cerevisiae. EUKARYOTIC CELL 2005; 4:1353-63. [PMID: 16087740 PMCID: PMC1214535 DOI: 10.1128/ec.4.8.1353-1363.2005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mid1 is a putative stretch-activated Ca2+ channel component and is required for the maintenance of viability in the mating process. In response to mating pheromone, the mid1 mutant normally forms a pointed mating projection but eventually dies. This phenotype is called the mid phenotype. To identify a protein regulating Mid1 or regulated by Mid1, we isolated a multicopy suppressor that rescues the mid1-1 mutant from mating pheromone-induced death and found that it encodes a truncated Spa2 protein lacking an amino-terminal region responsible for interaction with components of the mitogen-activated protein kinase cascades. One of these SPA2 alleles was SPA2DeltaN, whose product lacked the region from Ser5 to Leu230. SPA2DeltaN on a multicopy plasmid (YEpSPA2DeltaN) complemented the mid phenotype but not another phenotype, low Ca2+ accumulation, of the mid1-1 mutant. Neither SPA2DeltaN on a low-copy plasmid nor wild-type SPA2 on a multicopy plasmid had suppressive activity. The SPA2 gene is involved in the formation of a pointed mating projection, and cells of the spa2Delta mutant lacking Spa2 are viable and develop a peanut shell-like structure when exposed to mating pheromone. Like the spa2Delta mutant, the mid1-1 spa2Delta double mutant and the mid1-1/YEpSPA2DeltaN strain developed the peanut shell-like structure. The mid1-1 spa2Delta double mutant did not have the mid phenotype, indicating that SPA2 is epistatic to MID1. Overexpression of Spa2DeltaN abolished the localization of Spa2-green fluorescent protein to the tip of the mating projection. These results suggest that the Spa2DeltaN protein interferes with the localization of the normal Spa2 protein and thereby prevents cells from entering the mating process. Therefore, we suggest that Mid1 function is influenced by Spa2 function through polarized morphogenesis.
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Affiliation(s)
- Shigeko Noma
- Department of Biology, Tokyo Gakugei University, Tokyo 184-8501, Japan
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99
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Wang YJ, Yu JN, Chen T, Zhang ZG, Hao YJ, Zhang JS, Chen SY. Functional analysis of a putative Ca2+ channel gene TaTPC1 from wheat. JOURNAL OF EXPERIMENTAL BOTANY 2005; 56:3051-60. [PMID: 16275671 DOI: 10.1093/jxb/eri302] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The cytosolic free-calcium concentration [Ca2+](cyt) transiently increases under abiotic stresses and the proteins that control this process are gradually disclosed. The Ca2+-permeable channel is one type of these proteins in plants. In the present study, a novel Ca2+-permeable channel gene TaTPC1 encoding a putative membrane protein was cloned from wheat. It was induced under high salinity, polyethylene glycol, low temperature (4 degrees C), and abscisic acid. Expression of TaTPC1 in the yeast mutant lacking CCH1 can recover its growth under lithium stress through functional complementation. TaTPC1 transgenic plants exhibited more stomatal closing in the presence of Ca2+ than the control, supporting a role for the calcium channel in regulating plant responses to environmental change.
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Affiliation(s)
- Yu-Jun Wang
- National Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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100
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Peiter E, Fischer M, Sidaway K, Roberts SK, Sanders D. The Saccharomyces cerevisiae Ca2+ channel Cch1pMid1p is essential for tolerance to cold stress and iron toxicity. FEBS Lett 2005; 579:5697-703. [PMID: 16223494 DOI: 10.1016/j.febslet.2005.09.058] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Revised: 09/20/2005] [Accepted: 09/23/2005] [Indexed: 01/24/2023]
Abstract
Cch1p and Mid1p are components of a high-affinity Ca(2+)-permeable channel in the yeast plasma membrane. Here, we show that growth of mutants in the Cch1pMid1p channel is markedly hypersensitive to low temperature and to high iron concentration in the medium. Both phenotypes were suppressed by high Ca(2+) concentration. Iron stress elicited an increased Ca(2+) influx into both wild type and cch1Deltamid1Delta yeast. Inhibition of calcineurin strongly depressed growth of iron-stressed wild type yeast, indicating that calcineurin is a downstream element of the iron stress response. Iron hypersensitivity of the cch1Deltamid1Delta mutant was not associated with an increased iron uptake. An involvement of oxidative stress in the iron-hypersensitive phenotype was indicated by the findings that the antioxidants tocopheryl acetate and (ethyl)glutathione improved growth and viability of the iron-stressed mutant. Further, the degree of glutathione oxidation was increased in the presence of iron. The results indicate that iron stress leads to an increased oxidative poise and that Cch1pMid1p is essential to tolerate this condition.
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