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Knr4/Smi1 Family: Conserved Fungal Chaperones of Puzzling Origin
Hélène Martin-Yken, Mathias Richard, Jean François
To cite this version:
Hélène Martin-Yken, Mathias Richard, Jean François. Knr4/Smi1 Family: Conserved Fungal Chaper- ones of Puzzling Origin. Fungal Cell Wall Meeting 2012, May 2012, Primösten, Croatia. �hal-02951085�
Fungal Cell W all Biogenesis IV , Primösten, 2012
Knr4/Smi1 Family: Conserved Fungal Chaperones of Puzzling Origin
Hélène Martin-Yken 1 , Mathias L. Richard 2 & Jean François 1
1 Laboratory of Systems Engineering and Bioprocesses, LISBP, INSA, University of Toulouse, France, 2 INRA AgroParisTech, UMR1319 Micalis, Virulence et Infection Fongique, Thiverval-Grignon, France.
helene.martin@insa-toulouse.fr Tel: +33 5 61 55 99 59 http://www.lisbp.fr
We report here on the functional conservation of a family of fungal proteins, essentially involved in morphogenesis, cell wall synthesis and transcriptional control. The S. cerevisiae representant of this family, ScKrn4/Smi1has been the most studied and is a partially disordered protein.
A strinking characteristic of this protein is the vey high number of genetic and physical partners identified so far (233, www.yeastgenome.org).
Homologs of KNR4/SMI1 from various yeast species functionally complement phenotypes of the Saccharomyces cerevisiae knr4 null mutant, notably the genes from Candida albicans and Ashbya gossypii (also known as Eremothecium gossypii). The human pathogen C. albicans possesses 2 orthologs to ScKNR4/SMI1: SMI1 and SMI1B. Separate deletions of the two coding genes have been conducted and show different phenotypes (see below). The products of other homolog genes from more distant fungal species may not complement ScKnr4 function, but still display strikingly similar roles related to cell wall synthesis and cellular localization during growth (ex: Neurospora crassa GS1).
CONCLUSION :
Our results indicate that members of the KNR4/SMI1 gene family code for a group of chaperones, unique in the fungal kingdom, whose particular structural characteristics provide the ability to interact with several partners and to ensure a specific and conserved role in cellular morphogenesis and transcriptional control of cell wall synthesis genes. The cellular localization of these proteins during polarised growth is also characteristic and seems remarkably conserved among fungi. According to a recent structure similarity study, this gene family could originate from bacteria, and may have reached the eukaryote kingdom through viruses (Zhang, et al. Nucleic Acids Research, 4532-52 2011).
ScKnr4/Smi1: an Intrinsically Unfolded Protein :
PEST sequences, Interactions
inhibition (most of the protein biological function)
Essential when PKC1 pathway is disrupted, for interaction with calcineurin and
calcineurin activity
N-term: poorly
structured Structured and globular C-term: unstructured
1 80 340 505
Ca Smi1 and Smi1B :
Confocal fluorescence microscopy of GS-1-GFP, scale bar 5 μm.
Neurospora crassa GS-1 :
GS-1 gene, the Neurospora crassa homolog of ScKNR4/SMI1, was identified by complementation of a cell wall deficent mutant. GS-1 is required for the synthesis of b-1,3-glucan. (GS for Glucan Synthase, Enderlin and Selitrennikoff, PNAS USA 91, 9500-4, 1994).
GS-1 protein localizes at the tip of N. crassa growing hyphae, as a sphere around the « Spitzenkörper » , a strucure essential for hyphae growth which acts as a vesicle supply center. (Verdin et al., Mol Microbiol 74,
1044-53, 2009).
Even though the localization of N. crassa GS-1 and S. cerevisiae Knr4/Smi1 appears very similar, the two proteins may not be fonctionnally identical. Indeed, only the central domain (between aa 79 to 342 of ScKnr4), seems really well
conserved between the two proteins, especially residues 219 to 303 which reach 57% identity. The N- and C-terminal domains, responsible for the interaction with proteic partners in ScKnr4, are more divergent.
The mutant smi1-/- shows a clear hypersensitivity to CFW or SDS treatment, whereas smi1B-/- is unaffected by SDS and only slightly affected by CFW. In addition, C. albicans SMI1 gene, whose expression is induced in hyphal cells, is required for biofilm b-1,3-glucan matrix production and development of the associated drug resistance phenotype (ex: to flukonazole; Nett, et al., Curr.
Opin. Microbiol. 9, 340-345, 2011).
Complementation of knr4 D mutant in S. cerevisiae :
+ + + +
+ +
-
-
+ + +
Fungal homologs of Knr4 :
Cellular localization of ScKnr4/Smi1
During vegetative growth:
Knr4-GFP
And shmoo formation:
Haploid cells of mating type a, exposed to a pheromone for:
Knr4-GFP
1 hour 2 hours 3 hours
Data from our team :
Martin-Yken et al., 2003, Mol. Microbiol. 49, 23-35.
Basmaji et al., 2006, Mol Gen.Genomics, 275, 217-30.
Durand et al., 2008, Yeast, 25(8):563-76.
Dagkessamanskaia et al., 2010, Yeast, 27(8), 563-74.
And global studies :
Ito T. et al., 2001 PNAS U S A.; 98, 4277-8.
Goehring AS. et al., 2003 Mol Biol Cell. 14, 1501-16.
Tong, A. H.,et al., 2001, Science 294, 2364-8.
Uetz, P. et al., 2000. Nature 403, 623-627.
CWI pathway Polarisome
Calcineurin pathway
Stress /
Transcription
Bck1
Pkc1
Swi6
Bas1
Rpc40
Adh1 Snf2
Swi5 Mkk1
Swi3 Pho2
Gin4 Gcn1 Spa2
Rlm1
Bni1
Bem4 Slt2
Bud6
Rho1
Rpo31
Rom1 Pda1
Bem2 Cna1 Cnb1 Cna2
Crz1
Smi1/
Knr4
Cin5 Bem1
