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An Amyloid Core Sequence in the Major Candida albicans Adhesin Als1p Mediates Cell-Cell Adhesion.
mBio ( IF 6.4 ) Pub Date : 2019-10-08 , DOI: 10.1128/mbio.01766-19
Vida Ho 1 , Philippe Herman-Bausier 2 , Christopher Shaw 1 , Karen A Conrad 1 , Melissa C Garcia-Sherman 3 , Jeremy Draghi 3 , Yves F Dufrene 2 , Peter N Lipke 3 , Jason M Rauceo 4
Affiliation  

The human fungal commensal Candida albicans can become a serious opportunistic pathogen in immunocompromised hosts. The C. albicans cell adhesion protein Als1p is a highly expressed member of a large family of paralogous adhesins. Als1p can mediate binding to epithelial and endothelial cells, is upregulated in infections, and is important for biofilm formation. Als1p includes an amyloid-forming sequence at amino acids 325 to 331, identical to the sequence in the paralogs Als5p and Als3p. Therefore, we mutated Val326 to test whether this sequence is important for activity. Wild-type Als1p (Als1pWT) and Als1p with the V326N mutation (Als1pV326N) were expressed at similar levels in a Saccharomyces cerevisiae surface display model. Als1pV326N cells adhered to bovine serum albumin (BSA)-coated beads similarly to Als1pWT cells. However, cells displaying Als1pV326N showed visibly smaller aggregates and did not fluoresce in the presence of the amyloid-binding dye Thioflavin-T. A new analysis tool for single-molecule force spectroscopy-derived surface mapping showed that statistically significant force-dependent Als1p clustering occurred in Als1pWT cells but was absent in Als1pV326N cells. In single-cell force spectroscopy experiments, strong cell-cell adhesion was dependent on an intact amyloid core sequence on both interacting cells. Thus, the major adhesin Als1p interacts through amyloid-like β-aggregation to cluster adhesin molecules in cis on the cell surface as well as in trans to form cell-cell bonds.IMPORTANCE Microbial cell surface adhesins control essential processes such as adhesion, colonization, and biofilm formation. In the opportunistic fungal pathogen Candida albicans, the agglutinin-like sequence (ALS) gene family encodes eight cell surface glycoproteins that mediate adherence to biotic and abiotic surfaces and cell-cell aggregation. Als proteins are critical for commensalism and virulence. Their activities include attachment and invasion of endothelial and epithelial cells, morphogenesis, and formation of biofilms on host tissue and indwelling medical catheters. At the molecular level, Als5p-mediated cell-cell aggregation is dependent on the formation of amyloid-like nanodomains between Als5p-expressing cells. A single-site mutation to valine 326 abolishes cellular aggregation and amyloid formation. Our results show that the binding characteristics of Als1p follow a mechanistic model similar to Als5p, despite its differential expression and biological roles.

中文翻译:

主要白色念珠菌粘附素Als1p中的淀粉样蛋白核心序列介导细胞间粘附。

人类真菌共生白色念珠菌可在免疫功能低下的宿主中成为严重的机会病原体。白色念珠菌细胞粘附蛋白Als1p是一大类旁系粘附素的高表达成员。Als1p可以介导与上皮细胞和内皮细胞的结合,在感染中上调,并且对于生物膜形成很重要。Als1p在第325至331位氨基酸处包含淀粉样蛋白形成序列,与旁系同源物Als5p和Als3p中的序列相同。因此,我们对Val326进行了突变,以测试该序列对活性是否重要。野生型Als1p(Als1pWT)和具有V326N突变的Als1p(Als1pV326N)在酿酒酵母表面展示模型中以相似的水平表达。Als1pV326N细胞与Als1pWT细胞相似地粘附在牛血清白蛋白(BSA)包被的磁珠上。然而,展示Als1pV326N的细胞显示出明显较小的聚集体,并且在存在淀粉样蛋白结合染料硫黄素-T的情况下不发出荧光。一种用于单分子力谱的表面映射的新分析工具表明,具有统计学意义的依赖于力的Als1p簇发生在Als1pWT细胞中,而在Als1pV326N细胞中却不存在。在单细胞力谱实验中,强的细胞间粘附力取决于两个相互作用细胞上完整的淀粉样蛋白核心序列。因此,主要的粘附素Als1p通过类淀粉样β聚集相互作用,使粘附素分子在细胞表面的顺式和反式形成簇状,从而形成细胞-细胞键。重要信息微生物细胞表面的粘附素控制着重要的过程,例如黏附,定植,和生物膜形成。在机会性真菌病原体白色念珠菌中,凝集素样序列(ALS)基因家族编码八个介导对生物和非生物表面的粘附以及细胞-细胞聚集的细胞表面糖蛋白。Als蛋白对于共鸣和毒力至关重要。它们的活动包括内皮和上皮细胞的附着和侵袭,形态发生以及在宿主组织和留置医疗导管上形成生物膜。在分子水平上,Als5p介导的细胞间聚集取决于表达Als5p的细胞之间淀粉样样纳米域的形成。缬氨酸326的单点突变消除了细胞聚集和淀粉样蛋白的形成。我们的结果表明,Als1p的结合特征遵循类似于Als5p的机制模型,
更新日期:2019-11-01
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