Identification of human whole saliva protein components using proteomics

Abstract

The determination of salivary biomarkers as a means of monitoring general health and for the early diagnosis of disease is of increasing interest in clinical research. Based on the linkage between salivary proteins and systemic diseases, the aim of this work was the identification of saliva proteins using proteomics. Salivary proteins were separated using two-dimensional (2-D) gel electrophoresis over a pH range between 3-10, digested, and then analyzed by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF)-TOF mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Proteins were identified using automated MS and MS/MS data acquisition. The resulting data were searched against a protein database using an internal Mascot search routine. Ninety spots give identifications with high statistical reliability. Of the identified proteins, 11 were separated and identified in saliva for the first time using proteomics tools. Moreover, three proteins that have not been previously identified in saliva, PLUNC, cystatin A, and cystatin B were identified.

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).…”

“…In this frame, nearly 30 spots might be associated to unglycosylated forms, and at least 20 spots to glycosylated forms. Thus, α-amylase appears to display a diversity which is far larger than previously reported (7,20,21 (18). For most α-amylase spots that are observed at various MW lower than expected, other mechanisms must be taken into account.…”

“…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.…”