Attenuation of store-operated Ca ²⁺ current impairs salivary gland fluid secretion in TRPC1(−/−) mice

Abstract

Agonist-induced Ca 2؉ entry via store-operated Ca 2؉ (SOC) channels is suggested to regulate a wide variety of cellular functions, including salivary gland fluid secretion. However, the molecular components of these channels and their physiological function(s) are largely unknown. Here we report that attenuation of SOC current underlies salivary gland dysfunction in mice lacking transient receptor potential 1 (TRPC1). Neurotransmitter-regulated salivary gland fluid secretion in TRPC1-deficient TRPC1(؊/؊) mice was severely decreased (by 70%). Further, agonist-and thapsigargin-stimulated SOC channel activity was significantly reduced in salivary gland acinar cells isolated from TRPC1(؊/؊) mice. Deletion of TRPC1 also eliminated sustained Ca 2؉ -dependent potassium channel activity, which depends on Ca 2؉ entry and is required for fluid secretion. Expression of key proteins involved in fluid secretion and Ca 2؉ signaling, including STIM1 and other TRPC channels, was not altered. Together, these data demonstrate that reduced SOC entry accounts for the severe loss of salivary gland fluid secretion in TRPC1(؊/؊) mice. Thus, TRPC1 is a critical component of the SOC channel in salivary gland acinar cells and is essential for neurotransmitter-regulation of fluid secretion. transient receptor potential ͉ canonical ͉ Ca 2ϩ entry ͉ acinar cells ͉ muscarinic receptor

TRPV4 channel participates in receptor-operated calcium entry and ciliary beat frequency regulation in mouse airway epithelial cells

“…At this low ATP concentration, the Ca 2ϩ signal in tracheal cells is mainly oscillatory, a pattern that, at least for HEK cells, has been associated with the activity of store-operated pathways involving STIM1 and ORAI1 proteins without major contribution of TRP channels (43). Participation of TRPV4 in ciliated tracheal cells ROCE contrasts with the impact of TRPC1 in the Ca 2ϩ homeostasis of salivary gland epithelia, where it clearly affects both ROCE and SOCE (44). TRPC1, because all TRPCs except TRPC7, required STIM1 for its activation by receptor stimulation (45).…”

Extracellular Ca2+ Sensing in Salivary Ductal Cells

“…Fluorescence measurements were made using a Till Photonics-Polychrome IV spectrofluorometer and MetaFluor Imaging System (Universal Imaging Corporation). Fura-2 fluorescence in freshly dispersed submandibular cells was measured as described earlier (20,21) using an Olympus 50ϫ microscope, with an ORCA-ER camera (Hamamatsu) attached to a Polychrome IV (Till Photonics LLC). Ducts and acinar cells from the same glands were morphologically identified by their distinctive appearance under microscopic examination (22,23 Fully polarized monolayers were achieved at 72-96 h after cell plating.…”

“…Although the preparation contained both ductal fragments and acini, Ca 2ϩ measurements were made only in ducts (selected by imaging, see inset in Fig. 1B) (20,21). The function of CSR was examined by application of the potent agonist Gd 3ϩ (200 M) to cells in a Ca 2ϩ -free medium (Fig.…”

Thapsigargin activates Ca2+ entry both by store-dependent, STIM1/Orai1-mediated, and store-independent, TRPC3/PLC/PKC-mediated pathways in human endothelial cells

“…During the last 20 years, the family of TRPC (canonical transient receptor potential) channels has been proposed as candidates for SOCE. Number of reports has shown a reduced SOCE activity when TRPC expression was knocked down or knocked out [8][9][10][11]. When exogenously expressed some TRPC channels displayed SOCE activity [12][13][14].…”