Shared and Unique Proteins in Human, Mouse and Rat Saliva Proteomes: Footprints of Functional Adaptation

Abstract

The overall goal of our study was to compare the proteins found in the saliva proteomes of three mammals: human, mouse and rat. Our first objective was to compare two human proteomes with very different analysis depths. The 89 shared proteins in this comparison apparently represent a core of highly-expressed human salivary proteins. Of the proteins unique to each proteome, one-half to 2/3 lack signal peptides and probably are contaminants instead of less highly-represented salivary proteins. We recently published the first rodent saliva proteomes with salivas collected from the genome mouse (C57BL/6) and the genome rat (BN/SsNHsd/Mcwi). Our second objective was to compare the proteins in the human proteome with those we identified in the genome mouse and rat to determine those common to all three mammals as well as the specialized rodent subset. We also identified proteins unique to each of the three mammals because differences in the secreted protein constitutions can provide clues to differences in the evolutionary adaptation of the secretions in the three different mammals.

Comparative Proteomics of Mouse Tears and Saliva: Evidence from Large Protein Families for Functional Adaptation

“…The mouse saliva proteome was previously published [13,14]. We provided the dialyzed and concentrated tear fluids to the University of Arizona Proteomics Core Facility where personnel determined the protein quantity in the samples and performed single-dimension (1D) SDS gel separations and two-dimension (2D; isoelectric focusing × SDS gel electrophoresis) gel separations of equal protein quantities for each gender.…”

“…The discovery and description of three large protein families that influence mouse communication have arisen from our studies of mouse Androgen-Binding Proteins (ABPs; [15]), studies of Exocrine Secreted Peptides (ESPs; [16]) and studies of Major Urinary Proteins (MUPs; [17,18]) by other laboratories. We show that these mouse protein families are represented to varying degrees in the mouse tear proteome (this report) and the mouse saliva proteome [13,14], and yet the studies cited above have shown that these protein families have no counterparts in humans. We discuss the possibility that some of the proteins unique to each secretion represent important adaptations of the mouse tear and saliva protein complements, especially with respect to mouse communication.…”

“…We recently produced the saliva proteome of the genome mouse (C57BL/6) and the genome rat (BN/SsNHsd/Mcwi) using multidimensional protein identification technology (MUDPIT) for the purpose of studying rapidly evolving proteins and their genes [13,14]. In the original study, we focused on the independent expansions of the mouse and rat kallikrein subfamilies expressed in saliva and asked how selection influenced their evolution [14].…”

Salivary Mucin 19 Glycoproteins

“…Because Muc19 alone has very little aggregating activity, Muc19 must participate indirectly to aggregate S. mutans, likely through formation of heterotypic complexes with other salivary constituents that bind S. mutans. At least 38 human salivary proteins (those with a predicted signal peptide) have orthologs or paralogs in saliva of mice and/or rats (103). Unique to human saliva are additional proteins, including statherin-like proline-rich proteins, histatins, lysozyme, zinc ␣-glycoprotein, and the Ig saliva secretory complex (103).…”

“…Unique to human saliva are additional proteins, including statherin-like proline-rich proteins, histatins, lysozyme, zinc ␣-glycoprotein, and the Ig saliva secretory complex (103). The 22 proteins unique to mice are thought to be involved mostly in wound healing, identification, or grooming (103).…”