Diversity of GPI-anchored fungal adhesins

Abstract

Selective adhesion of fungal cells to one another and to foreign surfaces is fundamental for the development of multicellular growth forms and the successful colonization of substrates and host organisms. Accordingly, fungi possess diverse cell wall-associated adhesins, mostly large glycoproteins, which present N-terminal adhesion domains at the cell surface for ligand recognition and binding. In order to function as robust adhesins, these glycoproteins must be covalently linkedto the cell wall via C-terminal glycosylphosphatidylinositol (GPI) anchors by transglycosylation. In this review, we summarize the current knowledge on the structural and functional diversity of so far characterized protein families of adhesion domains and set it into a broad context by an in-depth bioinformatics analysis using sequence similarity networks. In addition, we discuss possible mechanisms for the membrane-to-cell wall transfer of fungal adhesins by membrane-anchored Dfg5 transglycosidases.

A targeted bioinformatics approach identifies highly variable cell surface proteins that are unique to Glomeromycotina

“…( b) Flexible cell wall locations. AGLs can potentially exist in any one, or all of the following extracellular locations due to the presence of a GPI-anchor: attached to the outer leaflet of the plasma membrane (PM), soluble (after cleavage of GPI-anchor), or potentially covalently linked to the cell wall (CW) (Essen et al 2020 ). CP, cytoplasm.…”

“…( c) “Cell–cell” interactions. AGLs could participate in cell–cell or cell-substrate adhesion (Essen et al 2020 ) generally and/or more specifically for self-recognition as occurs during anastomoses in AMF (Chagnon et al 2013 ). ( d) Wall adaptability.…”

Transposable elements in the genome of the lichen-forming fungus Umbilicaria pustulata, and their distribution in different climate zones along elevation

“…via targeted transcriptomic and proteomic analyses, to test whether and how they influence adaptation of the lichen ecotype to different climatic niches. Particularly interesting in this regard could be the effects of TEs inserted near i) genes involved in cell wall biosynthesis : a Copia element near a putative GPI ethanolamine phosphate gene, controlling membrane-to-cell wall transfer of fungal adhesins by membrane-anchored transglycosidases (68); a TIR element near Sac7 , a known activator of the small GTPase RHO1 , which plays an essential role in the control of cell wall synthesis and organization of the actin cytoskeleton (69); ii) genes involved in nutrient assimilation : a Copia element near a NADP-specific glutamate dehydrogenase, a key enzyme in the assimilation of alternative nitrogen sources through ammonium (70); an Helitron element near an acid protease, whose secretion grants access to the carbon and mineral nutrients within proteins in the cells of the plant host in fungal endophytes (71); an unknown TE element inserted near an inositol-pentakisphosphate 2-kinase, an enzyme involved in the decomposition of organic phosphates, whose activity is modulated by environmental pH (72); iii) genes involved in DNA repair mechanisms : a Copia element near a putative DNA glycosylase, a gene involved in single-base excision repair mechanisms (73); iv) genes involved in reproduction and environmental sensing : an unknown TE element located near a conidiation-specific gene, which plays a role in balancing asexual and sexual development, a process regulated by several factors including light, temperature, humidity, and nutrient availability (74,75); v) genes involved in secondary metabolism : a PiggyBac element within a type-I polyketide gene cluster containing fixed nonsense mutations in its core biosynthetic gene only in the cold-temperate climate zone (76). TEs have been previously identified as regulators of biosynthetic gene clusters in ascomycetes: the lower expression of the penicillin cluster in Aspergillus nidulans in the absence of Pbla element is a typical example (77).…”

FLO11, a Developmental Gene Conferring Impressive Adaptive Plasticity to the Yeast Saccharomyces cerevisiae

“…However, Flo11p possesses at its C-terminus two β-aggregation sequences that nicely match the amyloid-core sequence In contrast, the structural analysis of the A-domain of Flo11p has revealed a fibronectin type III-like adhesion domain that does not have any mannose-binding sites [24]. Interestingly, this type of domain is found only in the ascomycetal orders of Saccharomycetales, and in the Flo11p of Komagataella pastoris (formerly known as Pichia pastoris [25]) although sharing only 32% homology with ScFlo11p [26]. Interestingly, this A-domain is present in up to three times in adhesins of the human pathogenic Candida lusitaniae and the wood-boring beetle associated fungus, Spasthasphora passalidarum [24].…”

“…The Flo11p harbors at its carboxyl terminal a typical GPI-attachment site "GAANIKVL-GNFMWLLLALPVVF" that is composed of the ω-site (G) at position 1346 followed by a hydrophobic-like sequence termed pro-peptide (aa 1347 to 1376) [49]. This attachment signal is cleaved off and replaced by a preformed GPI-anchor in the endoplasmic reticulum, which enables trafficking of the modified protein via the classical secretory pathway to end up at the plasma membrane as GPI-PMPs [26]. A still unresolved issue is how some of these GPI-PMPs are sorted into the cell walls to be covalently linked to β-1,6-glucan, which involves a transglycosylation mediated by a Dfg5 enzyme [50,51].…”