Hube B
Institute für Allgemeine Botanik, AMP III, Universität Hamburg, Germany.
Curr Top Med Mycol. 1996 Dec;7(1):55-69.
Evidence suggests that infections with the opportunistic yeast Candida albicans are caused by several factors. Among these virulence attributes, secreted aspartyl proteinases (Saps) are widely believed to play a role during pathogenesis. Sap isoenzymes are encoded by at least eight closely related SAP genes. Antigen-antibody studies provided evidence that Sap isoenzymes are expressed in vivo and experimental infections with proteinase deficient mutants suggested a role for Saps in the virulence of C. albicans. However, only one gene product, Sap2, has been characterized in detail. In vitro studies with purified Sap(2) suggested several possible host targets but the role of each Sap isoenzyme remains unclear. The expression pattern of SAP genes proposed that Sap isoenzymes are secreted simultaneously with morphological changes such as the yeast to hyphal transition or during phenotypic switching. In addition, extracellular proteolytic activity may affect adhesion to host cells and thus may help the fungus to persist on host surfaces and to penetrate into deeper tissue. This review will deal with secretory proteinases from C. albicans as putative virulence factors and will focus on the more recent molecular aspects of the proteinases and their genes. Insights into the genetic organization and regulation of the secreted proteinases suggest not only that these enzymes may act as virulence factors of C. albicans, but that the pathogenesis of this fungus is indeed complex and multifactorial.
有证据表明,机会性酵母白色念珠菌的感染是由多种因素引起的。在这些毒力特性中,分泌天冬氨酸蛋白酶(Saps)被广泛认为在发病机制中起作用。Sap同工酶由至少八个密切相关的SAP基因编码。抗原-抗体研究提供了证据,表明Sap同工酶在体内表达,并且用蛋白酶缺陷突变体进行的实验感染表明Saps在白色念珠菌的毒力中起作用。然而,只有一种基因产物Sap2得到了详细的表征。对纯化的Sap(2)进行的体外研究提出了几种可能的宿主靶点,但每种Sap同工酶的作用仍不清楚。SAP基因的表达模式表明,Sap同工酶与形态变化(如酵母向菌丝的转变或表型转换)同时分泌。此外,细胞外蛋白水解活性可能影响对宿主细胞的粘附,因此可能有助于真菌在宿主表面持续存在并渗透到更深的组织中。这篇综述将讨论白色念珠菌的分泌蛋白酶作为假定的毒力因子,并将重点关注蛋白酶及其基因的最新分子方面。对分泌蛋白酶的遗传组织和调控的深入了解不仅表明这些酶可能作为白色念珠菌的毒力因子,而且表明这种真菌的发病机制确实是复杂的和多因素的。