CHARACTERIZATION OF COMMON SALIVARY PROTEIN-1, A PRODUCT OF RAT SUBMANDIBULAR, SUBLINGUAL, AND PAROTID-GLANDS

We have isolated and characterized cDNA clones derived from a developm entally regulated neonatal rat submandibular gland salivary protein ge ne called ''common salivary protein 1'' (CSP1). Identical clones were also identified in cDNA libraries from adult male parotid, submandibul ar, and sublingual glands. CSP1 transcripts are at least 10-fold more abundant in the sublingual gland than in the submandibular or parotid glands. In situ hybridization and immunocytochemical localization demo nstrated the presence of CSP1 transcripts and proteins in sublingual g land serous demilune cells, parotid and submandibular gland intercalat ed duct cells, and in the type III (proacinar) cells of the neonatal s ubmandibular gland. This cell-type distribution is similar to that des cribed by Ball and colleagues (Ball, W. D., Hand, A. R., and Johnson, A. O. (1988) Dev. Biol. 125, 265-279) for the developmentally regulate d submandibular gland B1-immunoreactive proteins. Immunoblotting of sa livary secretion identified proteins of M(r) 20,000 in sublingual, 16, 000 in submandibular and 22,000 and 16,000 in parotid gland. The M(r) 20,000 sublingual and 22,000 parotid proteins represent N-glycosylated forms of a M(r) 16,000 apoprotein, suggesting that these salivary pro teins arise by post-translational modification of a common precursor.