Saliva performs a number of extremely important biological functions that are instrumental in maintaining oral health. It has been estimated that more than 5 million people in the US suffers from salivary gland dysfunction. Secretion of saliva is driven by concerted activities of a number of ion channels and transporters. Although, it is believed that calcium is the primary intracellular factor that regulates fluid secretion, the molecular mechanism involved in the regulation of cytosolic calcium is not clearly understood. This is primarily due to the lack of information regarding the mechanism of regulation of calcium channels present in salivary glands. Furthermore, no information is available as how increase in cytosolic calcium modulates saliva secretion. Moreover, in Sj"gren's syndrome patients, although the acinar tissues appear to be normal, they do not function properly and have a decreased calcium response to agonist-stimulation. This observation raises the possibility that calcium channels might be altered in this pathological condition. Results obtained from our awarded grant indicate that TRPC1 is the primary calcium channel in salivary glands and is intimately involved saliva secretion. To understand the regulation of TRPC1 channel we have shown that in human submandibular gland cells, TRPC1 interaction with STIM1, Cav1, and Orai1 dictates TRPC1 mediated calcium entry. Furthermore, these protein-protein interactions were confined to specific domains in the plasma membrane, however nothing is known if similar mechanisms are also present in vivo in salivary gland tissues. Therefore, in this renewal we intend to thoroughly characterize the role of cytosolic calcium in salivary gland function and to determine the relationship between transient receptor potential canonical (TRPC1) -1 and saliva secretion. The hypothesis of this study is that because calcium influx via TRPC1 plays a pivotal role in the physiological function of salivary glands, characterization of calcium channels in salivary glands will be important to understand the mechanism of saliva secretion, which could represent as drug targets in salivary gland dysfunction. We will coordinate our efforts in order to determine the functional significance of TRPC1 channel in regulating saliva secretion. We will also investigate the role of lipid rafts in the assembly/activation of the TRPC1 channel in mouse submandibular gland cells and will identify the mechanism involved in the regulation of TRPC1 via STIM1 and Orai1. The results of our studies are expected to provide new insights into the role of calcium channels and the molecular mechanism involved in saliva secretion. Greater understanding of these events responsible for saliva secretion will be important in elucidating new therapy for salivary gland dysfunctions.

Public Health Relevance

It has been estimated that more than 5 million people in the US suffer from salivary gland dysfunctions. Loss of salivary gland function is a limiting side-effect of numerous drugs, serious consequences of head and neck cancer treatment using radiation therapy, and also a frequent outcome of autoimmune diseases such as Sjgren's syndrome. Our current studies are focused on the function of calcium influx via the Transient Receptor Potential canonical-1 in modulating saliva secretion. We anticipate that elucidating the mechanism of calcium entry-mediated regulation of saliva secretion;will be important to understand salivary gland dysfunction. Furthermore, we will identify the signalplex necessary for TRPC1-mediated calcium entry and define the mechanism involved in regulating TRPC1 channel per se. Greater understanding of these events will not only be important for understanding saliva secretion, but will be important in elucidating new therapies for salivary gland dysfunctions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE017102-09
Application #
8664243
Study Section
Oral, Dental and Craniofacial Sciences Study Section (ODCS)
Program Officer
Melillo, Amanda A
Project Start
2005-09-01
Project End
2016-05-31
Budget Start
2014-06-01
Budget End
2015-05-31
Support Year
9
Fiscal Year
2014
Total Cost
$324,984
Indirect Cost
$89,488
Name
University of North Dakota
Department
Biochemistry
Type
Schools of Medicine
DUNS #
102280781
City
Grand Forks
State
ND
Country
United States
Zip Code
58202
Sun, Yuyang; Sukumaran, Pramod; Varma, Archana et al. (2014) Cholesterol-induced activation of TRPM7 regulates cell proliferation, migration, and viability of human prostate cells. Biochim Biophys Acta 1843:1839-50
Pani, Biswaranjan; Liu, Xibao; Bollimuntha, Sunitha et al. (2013) Impairment of TRPC1-STIM1 channel assembly and AQP5 translocation compromise agonist-stimulated fluid secretion in mice lacking caveolin1. J Cell Sci 126:667-75
Vohra, Pawan K; Thompson, Michael A; Sathish, Venkatachalem et al. (2013) TRPC3 regulates release of brain-derived neurotrophic factor from human airway smooth muscle. Biochim Biophys Acta 1833:2953-60
Sun, Yuyang; Selvaraj, Senthil; Varma, Archana et al. (2013) Increase in serum Ca2+/Mg2+ ratio promotes proliferation of prostate cancer cells by activating TRPM7 channels. J Biol Chem 288:255-63
Pani, Biswaranjan; Bollimuntha, Sunitha; Singh, Brij B (2012) The TR (i)P to Ca²? signaling just got STIMy: an update on STIM1 activated TRPC channels. Front Biosci (Landmark Ed) 17:805-23
Selvaraj, Senthil; Sun, Yuyang; Watt, John A et al. (2012) Neurotoxin-induced ER stress in mouse dopaminergic neurons involves downregulation of TRPC1 and inhibition of AKT/mTOR signaling. J Clin Invest 122:1354-67
Bollimuntha, Sunitha; Selvaraj, Senthil; Singh, Brij B (2011) Emerging roles of canonical TRP channels in neuronal function. Adv Exp Med Biol 704:573-93
Kost, Gina Chun; Selvaraj, Senthil; Lee, Young Bok et al. (2011) Clavulanic acid increases dopamine release in neuronal cells through a mechanism involving enhanced vesicle trafficking. Neurosci Lett 504:170-5
Selvaraj, Senthil; Sun, Yuyang; Singh, Brij B (2010) TRPC channels and their implication in neurological diseases. CNS Neurol Disord Drug Targets 9:94-104
Dasari, Bhanu; Prasanthi, Jaya R P; Marwarha, Gurdeep et al. (2010) The oxysterol 27-hydroxycholesterol increases ?-amyloid and oxidative stress in retinal pigment epithelial cells. BMC Ophthalmol 10:22

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