Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets
ABSTRACT An important feature associated with Candida albicans pathogenicity is its ability to switch between yeast and hyphal forms, a process in which CaRas1 plays a key role. CaRas1 is activated by the guanine nucleotide exchange factor (GEF) CaCdc25, triggering hyphal growth-related signaling pa...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2023-08-01
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| Series: | mBio |
| Subjects: | |
| Online Access: | https://journals.asm.org/doi/10.1128/mbio.00638-23 |
| _version_ | 1797730265520406528 |
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| author | José A. Manso Arturo Carabias Zsuzsa Sárkány José M. de Pereda Pedro José Barbosa Pereira Sandra Macedo-Ribeiro |
| author_facet | José A. Manso Arturo Carabias Zsuzsa Sárkány José M. de Pereda Pedro José Barbosa Pereira Sandra Macedo-Ribeiro |
| author_sort | José A. Manso |
| collection | DOAJ |
| description | ABSTRACT An important feature associated with Candida albicans pathogenicity is its ability to switch between yeast and hyphal forms, a process in which CaRas1 plays a key role. CaRas1 is activated by the guanine nucleotide exchange factor (GEF) CaCdc25, triggering hyphal growth-related signaling pathways through its conserved GTP-binding (G)-domain. An important function in hyphal growth has also been proposed for the long hypervariable region downstream the G-domain, whose unusual content of polyglutamine stretches and Q/N repeats make CaRas1 unique within Ras proteins. Despite its biological importance, both the structure of CaRas1 and the molecular basis of its activation by CaCdc25 remain unexplored. Here, we show that CaRas1 has an elongated shape and limited conformational flexibility and that its hypervariable region contains helical structural elements, likely forming an intramolecular coiled-coil. Functional assays disclosed that CaRas1-activation by CaCdc25 is highly efficient, with activities up to 2,000-fold higher than reported for human GEFs. The crystal structure of the CaCdc25 catalytic region revealed an active conformation for the α-helical hairpin, critical for CaRas1-activation, unveiling a specific region exclusive to CTG-clade species. Structural studies on CaRas1/CaCdc25 complexes also revealed an interaction surface clearly distinct from that of homologous human complexes. Furthermore, we identified an inhibitory synthetic peptide, prompting the proposal of a key regulatory mechanism for CaCdc25. To our knowledge, this is the first report of specific inhibition of the CaRas1-activation via targeting its GEF. This, together with their unique pathogen-structural features, disclose a set of novel strategies to specifically block this important virulence-related mechanism. IMPORTANCE Candida albicans is the main causative agent of candidiasis, the commonest fungal infection in humans. The eukaryotic nature of C. albicans and the rapid emergence of antifungal resistance raise the challenge of identifying novel drug targets to battle this prevalent and life-threatening disease. CaRas1 and CaCdc25 are key players in the activation of signaling pathways triggering multiple virulence traits, including the yeast-to-hypha interconversion. The structural similarity of the conserved G-domain of CaRas1 to those of human homologs and the lack of structural information on CaCdc25 has impeded progress in targeting these proteins. The unique structural and functional features for CaRas1 and CaCdc25 presented here, together with the identification of a synthetic peptide capable of specifically inhibiting the GEF activity of CaCdc25, open new possibilities to uncover new antifungal drug targets against C. albicans virulence. |
| first_indexed | 2024-03-12T11:41:45Z |
| format | Article |
| id | doaj.art-91a4ad11f5194a0d9e9376efb1dace40 |
| institution | Directory Open Access Journal |
| issn | 2150-7511 |
| language | English |
| last_indexed | 2024-03-12T11:41:45Z |
| publishDate | 2023-08-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | mBio |
| spelling | doaj.art-91a4ad11f5194a0d9e9376efb1dace402023-08-31T15:04:20ZengAmerican Society for MicrobiologymBio2150-75112023-08-0114410.1128/mbio.00638-23Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targetsJosé A. Manso0Arturo Carabias1Zsuzsa Sárkány2José M. de Pereda3Pedro José Barbosa Pereira4Sandra Macedo-Ribeiro5IBMC–Instituto de Biologia Molecular e Celular, Universidade do Porto , Porto, PortugalInstituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas-University of Salamanca , Salamanca, SpainIBMC–Instituto de Biologia Molecular e Celular, Universidade do Porto , Porto, PortugalInstituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas-University of Salamanca , Salamanca, SpainIBMC–Instituto de Biologia Molecular e Celular, Universidade do Porto , Porto, PortugalIBMC–Instituto de Biologia Molecular e Celular, Universidade do Porto , Porto, PortugalABSTRACT An important feature associated with Candida albicans pathogenicity is its ability to switch between yeast and hyphal forms, a process in which CaRas1 plays a key role. CaRas1 is activated by the guanine nucleotide exchange factor (GEF) CaCdc25, triggering hyphal growth-related signaling pathways through its conserved GTP-binding (G)-domain. An important function in hyphal growth has also been proposed for the long hypervariable region downstream the G-domain, whose unusual content of polyglutamine stretches and Q/N repeats make CaRas1 unique within Ras proteins. Despite its biological importance, both the structure of CaRas1 and the molecular basis of its activation by CaCdc25 remain unexplored. Here, we show that CaRas1 has an elongated shape and limited conformational flexibility and that its hypervariable region contains helical structural elements, likely forming an intramolecular coiled-coil. Functional assays disclosed that CaRas1-activation by CaCdc25 is highly efficient, with activities up to 2,000-fold higher than reported for human GEFs. The crystal structure of the CaCdc25 catalytic region revealed an active conformation for the α-helical hairpin, critical for CaRas1-activation, unveiling a specific region exclusive to CTG-clade species. Structural studies on CaRas1/CaCdc25 complexes also revealed an interaction surface clearly distinct from that of homologous human complexes. Furthermore, we identified an inhibitory synthetic peptide, prompting the proposal of a key regulatory mechanism for CaCdc25. To our knowledge, this is the first report of specific inhibition of the CaRas1-activation via targeting its GEF. This, together with their unique pathogen-structural features, disclose a set of novel strategies to specifically block this important virulence-related mechanism. IMPORTANCE Candida albicans is the main causative agent of candidiasis, the commonest fungal infection in humans. The eukaryotic nature of C. albicans and the rapid emergence of antifungal resistance raise the challenge of identifying novel drug targets to battle this prevalent and life-threatening disease. CaRas1 and CaCdc25 are key players in the activation of signaling pathways triggering multiple virulence traits, including the yeast-to-hypha interconversion. The structural similarity of the conserved G-domain of CaRas1 to those of human homologs and the lack of structural information on CaCdc25 has impeded progress in targeting these proteins. The unique structural and functional features for CaRas1 and CaCdc25 presented here, together with the identification of a synthetic peptide capable of specifically inhibiting the GEF activity of CaCdc25, open new possibilities to uncover new antifungal drug targets against C. albicans virulence.https://journals.asm.org/doi/10.1128/mbio.00638-23Ras-like protein 1cell division control protein 25X-ray crystallographysmall angle X-ray scatteringpolyQ |
| spellingShingle | José A. Manso Arturo Carabias Zsuzsa Sárkány José M. de Pereda Pedro José Barbosa Pereira Sandra Macedo-Ribeiro Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets mBio Ras-like protein 1 cell division control protein 25 X-ray crystallography small angle X-ray scattering polyQ |
| title | Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets |
| title_full | Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets |
| title_fullStr | Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets |
| title_full_unstemmed | Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets |
| title_short | Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets |
| title_sort | pathogen specific structural features of candida albicans ras1 activation complex uncovering new antifungal drug targets |
| topic | Ras-like protein 1 cell division control protein 25 X-ray crystallography small angle X-ray scattering polyQ |
| url | https://journals.asm.org/doi/10.1128/mbio.00638-23 |
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