1 / 18

Overview

Join Nisha D’Silva, DDS, PhD, on June 3, 2002, for a detailed exploration of the cell biology behind salivary protein secretion in BMS 513. Delve into protein synthesis, secretory pathways, and signaling mechanisms involved in regulated secretion. Understand the synthesis, storage, and exocytosis of macromolecules in different salivary glands—sublingual, parotid, and submandibular. Discover the complex processes of protein movement, storage in secretory vesicles, and release through various secretory pathways like constitutive and regulated exocytosis. Gain insights into the control mechanisms of protein secretion through G-proteins, second messengers, and crosstalk between signaling pathways. Explore the effects of drugs like Propranolol, Pilocarpine, and Atropine on salivary secretion. Don’t miss this opportunity to enhance your understanding of salivary protein secretion mechanisms!

lcaldwell
Download Presentation

Overview

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cell Biology of Salivary Protein SecretionBiology of salivary glands (BMS 513)Nisha D’Silva DDS, PhDMonday, June 3, 20029 - 10 am, Rm G322

  2. Overview 1. Review anatomy and Histology 2. Secretory pathways 3. Signaling mechanism in regulated secretion. 4. Brief discussion about drugs and saliva.

  3. Macromolecule secretion • Polypeptides and proteins are synthesized and secreted by the salivary acinar cells • Sublingual saliva -- very thick and viscous • produced by mucous acinar cells • Parotid saliva -- thin and watery • produced by serous acinar cells • mainly salivary amylase and proline-rich polypeptides • Submandibular saliva -- intermediate consistency • a mix of serous and mucous acini

  4. Regardless of the type of protein • Too large to cross the cell membrane • Must be synthesized and stored within a membrane-bound vesicle and released by exocytosis

  5. Protein synthesis and secretory pathways

  6. Protein synthesis and secretion • Genes transcribed in nucleus to make mRNA • Message is transferred to ribosomes in cytoplasm • Secretory proteins begin with signal sequence which targets developing peptide to endoplasmic reticulum • At ER, peptide is N-glycosylated and folded into correct 3D structure • Small membrane vesicles carry proteins from ER through several layers of the golgi apparatus for additional processing and packaging for export

  7. Protein synthesis and secretion (cont’d) • Proteins move by default onwards from the ER • Specific retention sequences segregate non-secreted proteins • Secretory proteins are concentrated and stored in secretory vesicles • Mature vesicles are transported to apical membrane • Secretory stimuli result in vesicle fusion with plasma membrane • Contents of vesicles are discharged outside of cell

  8. Secretory pathways • 1. Constitutive - occurs continuously • 2. Regulated • 3. Paragranular - small vesicles break-off from SGs that undergo regulated secretion and are released

  9. Constitutive exocytosis • Differs from regulated exocytosis • Proteins not concentrated into secretory vesicles awaiting exocytotic stimulus • Continuous flow of protein in small vesicles to plasma membrane • Regulation occurs at synthesis stage

  10. Regulated secretion in salivary glands

  11. Mechanism of action of G- proteins

  12. Control of protein secretion: second messengers • Each stage of secretion is regulated by phosphorylation of target proteins • Phosphorylation is carried out by a protein kinase such as cyclic adenosine monophosphate (cAMP)-dependent protein kinase (protein kinase A) or PKC • cAMP stimulates maturation and translocation of secretory vesicles to the apical membrane • cAMP stimulates exocytosis

  13. Regulated secretion in salivary glands

  14. Four stages of cAMP production • Nordrenaline (NA) binds to -adrenergic receptors • G-protein (Gs) associated with the -adrenergic receptor moves to an active GTP-bound state • The Gs-GTP stimulates adenylate cyclase to convert ATP into cAMP • cAMP activates protein kinase A which phosphorylates target proteins

  15. Regulated secretion in salivary glands

  16. Crosstalk • Fluid and protein secretion occurs by different mechanisms controlled by different nerves • Separation between control of protein and electrolytes breaks down at second messenger level • Interaction between Ca2+ and cAMP-mediated events (cross-talk) allows combination of intracellular signaling pathways into an integrated stimulus-secretion coupling mechanism.

  17. Drugs and secretion 1. Propranolol (Inderal): -blocker 2. Pilocarpine (Salagen): cholinergic agonist parasympathetic pathway 3. Atropine: (Atropisol, Sal-Tropine) anti-cholinergic.

  18. Summary

More Related