CotHgenes are necessary for normal spore formation and virulence inMucor lusitanicus
Authors: Szebenyi Csilla , Gu Yiyou , Gebremariam Teclegiorgis , Kocsubé Sándor , Kiss-Vetráb Sándor , Jáger Olivér , Patai Roland , Spisák Krisztina , Sinka Rita , Binder Ulrike , Homa Mónika , Vágvölgyi Csaba , Ibrahim Ashraf S. , Nagy Gábor , Papp Tamás 
Published: December 2022

Mucormycosis is an invasive fungal infection caused by certain members of the fungal order of Mucorales. The species most frequently identified as the etiological agents of mucormycosis belong to the generaRhizopus, LichtheimiaandMucor. The frequency of systemic mucormycosis has been increasing, mainly because of the elevating numbers of susceptible patients. Furthermore, Mucorales display intrinsic resistance to the majority of routinely used antifungal agents (e.g., echinocandins and short-tailed azoles), which limits the number of possible therapeutic options. All the above-mentioned issues urge the improvement of molecular identification methods and the discovery of new antifungal targets and strategies. Spore coat proteins (CotH) constitute a kinase family present in many pathogenic bacteria and fungi and participate in the spore formation in these organisms. Moreover, some of them can act as virulence factors being receptors of the human GRP78 protein duringRhizopus delemar-induced mucormycosis. We identified 17cotH-likegenes in theMucor lusitanicusgenome database. Successful disruption of fivecotHgenes was performed using the CRISPR-Cas9 system inMucor. The CotH3 and CotH4 proteins play a role in adaptation to different temperatures as well as in developing the cell wall structure. We also show CotH4 protein is involved in spore wall formation by affecting the total chitin content and thus, the composition of the spore wall. Furthermore, we demonstrate that spore size is dependent on thecotH4gene. The role of CotH3 and CotH4 proteins in virulence was confirmed in two invertebrate models and DKA mouse model.

IMPORTANCE

Current treatment options for mucormycosis are inadequate resulting in high mortality rates especially among immunosuppressed patients. The development of novel therapies for mucormycosis has been hampered by lack of understanding of the pathogenetic mechanisms. The importance of the cell surface CotH proteins in the pathogenesis ofRhizopus-mediated mucormycosis has been recently described. However, the contribution of this family of proteins to the virulence of other mucoralean fungi and their functionality in vital processes remain undefined. Through the use of CRISPR-Case9 gene disruption system, we demonstrate the importance of several of the CotH proteins to the virulence ofMucor lusitanicusby using three infection models. We also report on the importance of one of these proteins, CotH4, to the spore wall formation through affecting the chitin content. Therefore, our studies extend the importance of CotH proteins toMucorand identifies the mechanism by which one of the CotH proteins contributes to the development of a normal fungal cell wall, thereby indicating that this family of proteins can be targeted for future development of novel therapeutic strategies of mucormycosis.