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Alexander AJT, Muñoz A, Marcos JF, Read ND. Calcium homeostasis plays important roles in the internalization and activities of the small synthetic antifungal peptide PAF26. Mol Microbiol 2020; 114:521-535. [PMID: 32898933 DOI: 10.1111/mmi.14532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 05/01/2020] [Accepted: 05/17/2020] [Indexed: 01/22/2023]
Abstract
Fungal diseases are responsible for the deaths of over 1.5 million people worldwide annually. Antifungal peptides represent a useful source of antifungals with novel mechanisms-of-action, and potentially provide new methods of overcoming resistance. Here we investigate the mode-of-action of the small, rationally designed synthetic antifungal peptide PAF26 using the model fungus Neurospora crassa. Here we show that the cell killing activity of PAF26 is dependent on extracellular Ca2+ and the presence of fully functioning fungal Ca2+ homeostatic/signaling machinery. In a screen of mutants with deletions in Ca2+ -signaling machinery, we identified three mutants more tolerant to PAF26. The Ca2+ ATPase NCA-2 was found to be involved in the initial interaction of PAF26 with the cell envelope. The vacuolar Ca2+ channel YVC-1 was shown to be essential for its accumulation and concentration within the vacuolar system. The Ca2+ channel CCH-1 was found to be required to prevent the translocation of PAF26 across the plasma membrane. In the wild type, Ca2+ removal from the medium resulted in the peptide remaining trapped in small vesicles as in the Δyvc-1 mutant. It is, therefore, apparent that cell killing by PAF26 is complex and unusually dependent on extracellular Ca2+ and components of the Ca2+ -regulatory machinery.
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Affiliation(s)
- Akira J T Alexander
- Institute of Infection, Immunity & Inflammation, The University of Glasgow, Glasgow, Scotland
| | - Alberto Muñoz
- MRC Centre for Medical Mycology, University of Exeter, Exeter, UK
| | - Jose F Marcos
- Department of Food Biotechnology, Instituto de Agroquímica y Tecnología de Alimentos (IATA) , Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain
| | - Nick D Read
- Manchester Fungal Infection Group, Infection, Immunity & Respiratory Medicine, University of Manchester, Manchester, UK
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Abstract
The growth and development of most fungi take place on a two-dimensional surface or within a three-dimensional matrix. The fungal sense of touch is therefore critical for fungi in the interpretation of their environment and often signals the switch to a new developmental state. Contact sensing, or thigmo-based responses, include thigmo differentiation, such as the induction of invasion structures by plant pathogens in response to topography; thigmonasty, where contact with a motile prey rapidly triggers its capture; and thigmotropism, where the direction of hyphal growth is guided by physical features in the environment. Like plants and some bacteria, fungi grow as walled cells. Despite the well-demonstrated importance of thigmo responses in numerous stages of fungal growth and development, it is not known how fungal cells sense contact through the relatively rigid structure of the cell wall. However, while sensing mechanisms at the molecular level are not entirely understood, the downstream signaling pathways that are activated by contact sensing are being elucidated. In the majority of cases, the response to contact is complemented by chemical cues and both are required, either sequentially or simultaneously, to elicit normal developmental responses. The importance of a sense of touch in the lifestyles and development of diverse fungi is highlighted in this review, and the candidate molecular mechanisms that may be involved in fungal contact sensing are discussed.
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Lew RR, Giblon RE, Lorenti MSH. The phenotype of a phospholipase C (plc-1) mutant in a filamentous fungus, Neurospora crassa. Fungal Genet Biol 2015. [PMID: 26212074 DOI: 10.1016/j.fgb.2015.07.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the filamentous fungus Neurospora crassa, phospholipase C may play a role in hyphal extension at the growing tips as part of a growth-sensing mechanism that activates calcium release from internal stores to mediate continued expansion of the hyphal tip. One candidate for a tip-localized phospholipase C is PLC-1. We characterized morphology and growth characteristics of a knockout mutant (KO plc-1) and a RIP mutated strain (RIP plc-1) (missense mutations and a nonsense mutation render the gene product non-functional). Growth and hyphal cytology of wildtype and KO plc-1 were similar, but the RIP plc-1 mutant grew slower and exhibited abnormal membrane structures at the hyphal tip, imaged using the fluorescence dye FM4-64. To test for causes of the slower growth of the RIP plc-1 mutant, we examined its physiological poise compared to wildtype and the KO plc-1 mutant. The electrical properties of all three strains and the electrogenic contribution of the plasma membrane H(+)-ATPase (identified by cyanide inhibition) were the same. Responses to high osmolarity were also similar. However, the RIP plc-1 mutant had a significantly lower turgor, a possible cause of its slower growth. While growth of all three strains was inhibited by the phospholipase C inhibitor 3-nitrocoumarin, the RIP plc-1 mutant did not exhibit hyphal bursting after addition of the inhibitor, observed in both wildtype and the KO plc-1 mutant. Although the plc-1 gene is not obligatory for tip growth, the phenotype of the RIP plc-1 mutant - abnormal tip cytology, lower turgor and resistance to inhibitor-induced hyphal bursting - suggest it does play a role in tip growth. The expression of a dysfunctional plc-1 gene may cause a shift to alternative mechanism(s) of growth sensing in hyphal extension.
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Affiliation(s)
- Roger R Lew
- York University, Biology Department, 4700 Keele Street, Toronto, ON M3J 1P3, Canada.
| | - Rachel E Giblon
- York University, Biology Department, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
| | - Miranda S H Lorenti
- York University, Biology Department, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
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Organellar mechanosensitive channels involved in hypo-osmoregulation in fission yeast. Cell Calcium 2014; 56:467-71. [PMID: 25454595 DOI: 10.1016/j.ceca.2014.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 10/01/2014] [Accepted: 10/04/2014] [Indexed: 01/26/2023]
Abstract
MscS and MscL, bacterial mechanosensitive channels, play crucial roles in the hypo-osmotic shock response. However, only MscS has homologs in eukaryotes. These homologs are called MscS-like proteins or MSL proteins. MSL proteins have changed both structurally and functionally during evolution and are now localized not only to the membrane of the chloroplast, which is thought to be a descendant of an ancient, free-living bacterium, but also the cell membrane and the endoplasmic reticulum (ER) membrane, suggesting that the role of MSL proteins has diverged. In this brief review, we mainly focus on two MSL proteins in the fission yeast Schizosaccharomyces pombe that are localized in the ER membrane and protect cells from hypo-osmotic shock-induced death by regulating intracellular Ca(2+) concentrations. We also discuss Arabidopsis thaliana MSL proteins and other yeast ion channels in terms of osmoregulation in eukaryotes.
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Gonçalves AP, Cordeiro JM, Monteiro J, Muñoz A, Correia-de-Sá P, Read ND, Videira A. Activation of a TRP-like channel and intracellular Ca2+ dynamics during phospholipase-C-mediated cell death. J Cell Sci 2014; 127:3817-29. [PMID: 25037570 PMCID: PMC4150065 DOI: 10.1242/jcs.152058] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The model organism Neurospora crassa undergoes programmed cell death when exposed to staurosporine. Here, we show that staurosporine causes defined changes in cytosolic free Ca2+ ([Ca2+]c) dynamics and a distinct Ca2+ signature that involves Ca2+ influx from the external medium and internal Ca2+ stores. We investigated the molecular basis of this Ca2+ response by using [Ca2+]c measurements combined with pharmacological and genetic approaches. Phospholipase C was identified as a pivotal player during cell death, because modulation of the phospholipase C signaling pathway and deletion of PLC-2, which we show to be involved in hyphal development, results in an inability to trigger the characteristic staurosporine-induced Ca2+ signature. Using Δcch-1, Δfig-1 and Δyvc-1 mutants and a range of inhibitors, we show that extracellular Ca2+ entry does not occur through the hitherto described high- and low-affinity Ca2+ uptake systems, but through the opening of plasma membrane channels with properties resembling the transient receptor potential (TRP) family. Partial blockage of the response to staurosporine after inhibition of a putative inositol-1,4,5-trisphosphate (IP3) receptor suggests that Ca2+ release from internal stores following IP3 formation combines with the extracellular Ca2+ influx.
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Affiliation(s)
- A Pedro Gonçalves
- IBMC-Instituto de Biologia Molecular e Celular - Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal ICBAS-Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - J Miguel Cordeiro
- ICBAS-Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - João Monteiro
- IBMC-Instituto de Biologia Molecular e Celular - Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal
| | - Alberto Muñoz
- Manchester Fungal Infection Group, Institute of Inflammation and Repair, CTF Building, Grafton Street, University of Manchester, Manchester M13 9NT, UK
| | - Paulo Correia-de-Sá
- ICBAS-Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Nick D Read
- Manchester Fungal Infection Group, Institute of Inflammation and Repair, CTF Building, Grafton Street, University of Manchester, Manchester M13 9NT, UK
| | - Arnaldo Videira
- IBMC-Instituto de Biologia Molecular e Celular - Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal ICBAS-Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
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