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Candida albicans Cell Wall Proteins

Candida albicans Cell Wall Proteins
W. LaJean Chaffin

Microbiology and Molecular Biology Reviews, September 2008, p. 495544,
Vol. 72, No. 3,10922172

Abstract:

Some secreted proteins do not remain cell associated but forage into the extracellular environment. If such
proteins are hydrolytic enzymes, they have capacity to hydrolyze large or complex substrates into small units that can be transported into the cell as a source of nutrition. If the degradation of host targets facilitates colonization or invasion, then such enzymes also function as virulence factors. In the last few years, several studies have examined clinical isolates for one or more phospholipase, proteinase, or hemolytic activities. These studies demonstrate the production of these activities by some but not all isolates. There are differences based on the site of isolation or the presence of type 2 diabetes mellitus. One of the characteristics of most of the hydrolytic activities is that there are multiple enzymes that may be expressed under different conditions.

Introduction:

The cell surface has two essential roles: to maintain the integrity of the cell and to interact with the environment. A rigid cell wall provides the surface that surrounds the cell. The surface is the contact point between the microbe and host surfaces including phagocytic cells. It may also be the target of antibody response. In addition, commensal microbes found in biofilms on mucosal surfaces or microbes in biofilms formed on medical devices and prostheses have surface interactions. For Candida albicans, the cell wall has been a consistent focus of attention over the last several decades. Keyword searches for "albicans," "albicans cell wall," and "albicans adherence" in PubMed (www.pubmed.gov) showed that total publications on C. albicans increased by over 50% in the decade between 1998 and 2007 from the previous decade (Table 1). The number of publications related to cell wall and adherence increased over the same period but decreased slightly as the proportion of the total reports. One area that has become more prominent in the last decade and that has a cell surface component is studies on C. albicans biofilm. In this area, there is a more-than-sixfold increase in the proportion of reported studies on biofilm. The availability of DNA sequences from the genomic sequencing project (162) applied to both individual genes and the whole genome, e.g., microarray generation and proteomics, has also contributed increasingly in this decade to studies of the cell surface from global and individual gene perspectives. Another characteristic of these reports not evident from these numbers appears to be a greater diversity or number of the proteins and functions examined. The study of C. albicans cell surface proteins is moving forward on a broad front utilizing a variety of tools.

An extensive review of C. albicans cell wall and exported proteins (49) appeared in 1998, and this review will focus on the most recent decade. During this decade, there have been multiple reviews on various aspects of the C. albicans cell surface, including several very recently (100, 101, 116, 187, 215, 246, 312, 322, 355, 381). The proteins of the cell wall may play a role in maintaining structural integrity and in mediating adherence, whether to host or microbes, or they may have enzymatic functions, e.g., proteolysis. Additional factors that may influence these proteins are the morphology of yeast cells, pseudohyphae, and hyphae and the maintenance of either a planktonic or a sessile lifestyle. This review is not a comprehensive discussion of every proposed cell surface and exported protein. The number of potential and demonstrated proteins of the cell surface is too large, as will be indicated later, to give each of these proteins individual attention. However, the number of proteins with suggested functions and proteins which when deleted affect the cell are much fewer in number. The individual proteins discussed are from this latter group. Gene names are those from Candida Genome Database (CGD; August 2007 [9]). After an overview of cell wall-associated proteins, the review will focus on many of the enzymatic activities and adherence interactions mediated by cell surface proteins of the fungus in vitro.

Full Text: http://mmbr.asm.org/cgi/content/full/72/3/495


Keywords: Candida albicans Cell Wall Proteins secreted proteins enzyme advanced

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