2 research outputs found
Bacterial Derived Carbohydrates Bind Cyr1 and Trigger Hyphal Growth in <i>Candida albicans</i>
The
dimorphic yeast <i>Candida albicans</i> is the most common
pathogenic fungus found in humans. While this species is normally
commensal, a morphological switch from budding yeast to filamentous
hyphae allows the fungi to invade epithelial cells and cause infections.
The phenotypic change is controlled by the adenylyl cyclase, Cyr1.
Interestingly, this protein contains a leucine-rich repeat (LRR) domain,
which is commonly found in innate immune receptors from plants and
animals. A functional and pure LRR domain was obtained in high yields
from <i>E. coli</i> expression. Utilizing a surface
plasmon resonance assay, the LRR was found to bind diverse bacterial
derived carbohydrates with high affinity. This domain is capable of
binding fragments of peptidoglycan, a carbohydrate polymer component
of the bacterial cell wall, as well as anthracyclines produced by <i>Streptomyces</i>, leading to hyphae formation. These findings
add another dimension to the human microbiome, taking into account
yeast–bacteria interactions that occur in the host
Crohn’s Disease Variants of Nod2 Are Stabilized by the Critical Contact Region of Hsp70
Nod2
is a cytosolic, innate immune receptor responsible for binding
to bacterial cell wall fragments such as muramyl dipeptide (MDP).
Upon binding, subsequent downstream activation of the NF-ÎşB
pathway leads to an immune response. Nod2 mutations are correlated
with an increased susceptibility to Crohn’s disease (CD) and
ultimately result in a misregulated immune response. Previous work
had demonstrated that Nod2 interacts with and is stabilized by the
molecular chaperone Hsp70. In this work, it is shown using purified
protein and <i>in vitro</i> biochemical assays that the
critical Nod2 CD mutations (G908R, R702W, and 1007fs) preserve the
ability to bind bacterial ligands. A limited proteolysis assay and
luciferase reporter assay reveal regions of Hsp70 that are capable
of stabilizing Nod2 and rescuing CD mutant activity. A minimal 71-amino
acid subset of Hsp70 that stabilizes the CD-associated variants of
Nod2 and restores a proper immune response upon activation with MDP
was identified. This work suggests that CD-associated Nod2 variants
could be stabilized <i>in vivo</i> with a molecular chaperone