A key event in the secretagogue stimulation of both the fluid and protein component of saliva is an increase in the cytosolic free calcium concentration [Ca2+].i This increase in [Ca2+]i has specific temporal and spatial characteristics which are important for appropriately activating effectors pivotal for the secretion of saliva. Acetylcholine and the majority of other secretagogues act in a metabotropic manner stimulating the production of inositol 1,4,5-trisphosphate (InsP3) and the release of intracellular Ca2+. In salivary acinar cells, Ca2+ signals can also be generated by an alternative, largely independent ionotropic process following adenosine triphosphate (ATP) activation of the P2X class of Ca2+ permeable ion channels. The latter mechanism would be predicted to result in Ca2+ signals and effector activation with distinct spatial and temporal characteristics. Using contempory optical techniques, such as digital imaging, total internal reflection microscopy and confocal microscopy combined with transgenic animal models and specific pharmacology we will expand on findings generated in isolated salivary gland acini to define Ca2+ signaling events stimulated through both metabotropic and in particular through the P2X4 purinergic receptor (P2X4R) in an organotypic parotid gland slice preparation (aim 1). Ca2+ signals as a result of P2X4R activation are profoundly enhanced following protein kinase A (PKA) activation. Since fluid secretion is also enhanced when PKA is activated this may be the physiologically relevant situation.
In specific aim 2 we propose to define the molecular mechanism underlying this event.
In specific aim 3 a primary goal will also be to assess whether ionotropic purinergic signaling through P2X4 receptors (P2X4R), either alone, or following specific pharmacological manipulation is an effective activator of the fluid and exocytotic secretion mechanism. These studies are designed to advance our understanding of the complex series of regulated molecular events which result in fluid secretion and may ultimately lead to the design of therapeutic strategies for the treatment of xerostomia based on exploiting the physiology of remaining functional acinar tissue. Saliva is vital for oral health. It is essential for the hydration of the oral mucosa;it provides lubrication, begins nutrient digestion and imparts antimicrobial and mechanical protection for the mouth and upper gastrointestinal tract. Reduced flow of saliva (xerostomia) greatly impacts the quality of life of sufferers. A key event in the secretagogue stimulation of both the fluid and protein component of saliva is an increase in the cytosolic free calcium concentration [Ca2+].i These studies are designed to advance our understanding of the complex series of regulated molecular events which result in the increase in [Ca2+]i and hence fluid secretion. Ultimately these data are designed to lead to the design of therapeutic strategies for the treatment of xerostomia based on exploiting the physiology of remaining functional acinar tissue.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE014756-09
Application #
8048136
Study Section
Oral, Dental and Craniofacial Sciences Study Section (ODCS)
Program Officer
Burgoon, Penny W
Project Start
2002-08-15
Project End
2012-05-31
Budget Start
2011-04-01
Budget End
2012-05-31
Support Year
9
Fiscal Year
2011
Total Cost
$368,925
Indirect Cost
Name
University of Rochester
Department
Pharmacology
Type
Schools of Dentistry
DUNS #
041294109
City
Rochester
State
NY
Country
United States
Zip Code
14627
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Wang, Liwei; Yule, David I (2018) Differential regulation of ion channels function by proteolysis. Biochim Biophys Acta Mol Cell Res :
Nurbaeva, Meerim K; Eckstein, Miriam; Devotta, Arun et al. (2018) Evidence That Calcium Entry Into Calcium-Transporting Dental Enamel Cells Is Regulated by Cholecystokinin, Acetylcholine and ATP. Front Physiol 9:801
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Wang, Liwei; Wagner 2nd, Larry E; Alzayady, Kamil J et al. (2018) Region-specific proteolysis differentially modulates type 2 and type 3 inositol 1,4,5-trisphosphate receptor activity in models of acute pancreatitis. J Biol Chem 293:13112-13124
Wang, Liwei; Wagner 2nd, Larry E; Alzayady, Kamil J et al. (2017) Region-specific proteolysis differentially regulates type 1 inositol 1,4,5-trisphosphate receptor activity. J Biol Chem 292:11714-11726
Gerber, Sylvie; Alzayady, Kamil J; Burglen, Lydie et al. (2016) Recessive and Dominant De Novo ITPR1 Mutations Cause Gillespie Syndrome. Am J Hum Genet 98:971-980
Chandrasekhar, Rahul; Alzayady, Kamil J; Wagner 2nd, Larry E et al. (2016) Unique Regulatory Properties of Heterotetrameric Inositol 1,4,5-Trisphosphate Receptors Revealed by Studying Concatenated Receptor Constructs. J Biol Chem 291:4846-60
Alzayady, Kamil J; Wang, Liwei; Chandrasekhar, Rahul et al. (2016) Defining the stoichiometry of inositol 1,4,5-trisphosphate binding required to initiate Ca2+ release. Sci Signal 9:ra35
Wang, Liwei; Alzayady, Kamil J; Yule, David I (2016) Proteolytic fragmentation of inositol 1,4,5-trisphosphate receptors: a novel mechanism regulating channel activity? J Physiol 594:2867-76

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