Proteome of human minor salivary gland secretion

Abstract

Recent research efforts in oral biology have resulted in elucidation of the proteomes of major human salivary secretions and whole saliva. One might hypothesize that the proteome of minor gland secretions may show significantly different characteristics when compared with the proteomes of parotid or submandibular/sublingual secretions. To test this hypothesis, we conducted the first exploration into the proteome of minor salivary gland secretion. Minor gland secretion was obtained from healthy volunteers, and its components were subjected to liquid-chromatography-electrospray-ionization-tandem-mass-spectrometry. This led to the identification of 56 proteins, 12 of which had never been identified in any salivary secretion. The unique characteristics of the minor salivary gland secretion proteome are related to the types as well as the numbers of components present. The differences between salivary proteomes may be important with respect to specific oral functions.

Figure 1

Summary of the distribution of 56 proteins identified from labial minor salivary gland secretion with 3 different sample preparations.

Figure 2

Base-peak chromatogram of one of the 12 fractions separated by cation exchange chromatography and analyzed by LC-ESI-MS/MS with a nano-flow reverse-phase HPLC column, with gradient elution ranging from 5 to 50% solvent B in 40 min (A). Cation exchange chromatogram of the tryptic peptides derived from proteins associated with labial minor salivary gland secretion (Inset). MS/MS spectrum and sequence analysis of a tryptic peptide. The sequence of R.TVQIAAVVDVIR.E led to the identification of "prolactin inducible protein" (P12273). Matching b- and y-ion series are indicated in the upper right (B).

Figure 3

Classification of labial minor salivary gland secretion proteins according to their origin (A) and their biological functions (B). Information on origin and biological function was derived from protein annotations. Proteins with more than one origin and more than one biological function were counted multiple times.

Figure 4

Relative proportions of major, minor, and novel salivary proteins in labial minor salivary gland secretion. *Histatin 1 was included based on the presence of the C-terminal 16-residue peptide found in all 3 sample preparations (A). MS/MS spectrum and sequence analysis of a tryptic peptide. The sequence of R.DPSQQELPR.L is indicative of the presence of "fatty acid synthase" (P49327). Matching b-and y-ion series are indicated in the upper right (B).