Saliva contains a broad spectrum of proteins which are known to play a pivotal role in maintaining the integrity of the hard and soft oral tissues. Many of the proteins secreted from the parotid gland are glycoproteins and carry N-linked oligosacchrides, so-called N-linked glycoproteins. To study the mechanisms involved in processing, synthesis and secretion of N-linked secretory glycoproteins, we have utilized in vitro cell and microsomal membrane preparations from rat parotid glands. We have shown that Beta-adrenergic receptor stimulation increases (3H)-mannose incorporation into newly synthesized glycoproteins by a cyclic AMP mediated mechanism. During the present reporting period we have 1) further characterized the procesing of oligosacchrides after beta-adrenoreceptor stimulation and demonstrated the effect of a glucosidase I, II inhibitor, deoxnejorimycin, on the maturation and secretion of parotid glycoproteins; 2) isolated fractions enriched in the four secretory glycoproteins (17, 32, 38 and 220 Kd) exhibiting glycosylation changes after Beta-adrenoreceptor stimulation and produced a polyclonal antiserum which reacts with all four; 3) observed increased activity of several dolichol-linked glycosyltransferases after Beta-adrenoreceptor stimulation and demonstrated that for one enzyme, Man-P-Dol synthase, a cyclic AMP-dependent protein kinase phosphorylation in vitro results in a kinetically identical activation as seen with Beta-adrenoreceptor stimulation in the intact cell; and 4) initiated investigations in vivo on the effects of beta-adrenergic receptor stimulation on functional properties of N-linked secretory glycoproteins.
