Mapping of proteins in human saliva using two‐dimensional gel electrophoresis and peptide mass fingerprinting

Abstract

Human saliva contains a large number of proteins that can be used for diagnosis and are of great potential in clinical and epidemiological research. The aim of this work was to map the proteins in saliva by two-dimensional gel electrophoresis (2-DE), and to identify abundant proteins by peptide mass fingerprinting using trypsin cleavage and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry analysis. One hundred proteins were identified representing 20 different identities according to accession numbers. Abundant proteins expressed in different forms were: alpha-amylase, immunoglobulin A, prolactin-inducible protein, zinc-alpha(2)-glycoprotein and cystatins (S, SA, D and SN). Other proteins found were interleukin-1 receptor antagonist, von Ebner's gland protein (lipocalin-1) and calgranulin A and B (S100A8 and A9). Furthermore, apolipoprotein A-I, beta(2)-microglobulin, glutathione S-transferase P and fatty acid-binding protein were also identified. Our results show that human saliva contains a large number of proteins that are involved in inflammatory and immune responses. The 2-DE protein map constructed opens the possibility to investigate protein changes associated with disease processes.

Complexity of the human whole saliva proteome

“…On this point of view, our results amplify the most recent saliva proteomic characterization (7,9,20) and do not support the previous conclusion that major proteins, such as α-amylase and albumin, display little if any modification (21).…”

“…Saliva is usually taken as a complex medium, that was recently characterized by proteomic approach (7,9,20,21), allowing the cumulated identification of up to 35 accessions.…”

“…A main feature raising from the 320 protein spots that were characterized in these works (7,9,20,21), is that the saliva proteome contains a relatively low number of different accessions, but, conversely, spread out over a large number of protein spots (Table II).…”

“…Accordingly, the saliva proteome was firstly shown to display a relatively simple pattern with 7 accessions identified in 10 protein spots (21). By opposition, in two other works, a much more complex situation was described (7,20). In these cases, 20 to 35 accessions were identified within one hundred of protein spots.…”

“…For others, like α-amylase, when the occurrence of isoforms is frequent (2), redundancy can not be ascribed from aforementioned post-translational modification nor protein degradation. In this case, an additional possible mechanism would rely on bacterial degradation (7). This could deeply affect any strategy in search for biological markers in clinical applications.…”