Calcium-activated chloride channel (CaCC) plays an important role in modulating 
epithelial secretion. It has been suggested that in salivary tissues, sustained 
fluid secretion is dependent on Ca(2+) influx that activates ion channels such 
as CaCC to initiate Cl(-) efflux. However direct evidence as well as the 
molecular identity of the Ca(2+) channel responsible for activating CaCC in 
salivary tissues is not yet identified. Here we provide evidence that in human 
salivary cells, an outward rectifying Cl(-) current was activated by increasing 
[Ca(2+)]i, which was inhibited by the addition of pharmacological agents 
niflumic acid (NFA), an antagonist of CaCC, or T16Ainh-A01, a specific TMEM16a 
inhibitor. Addition of thapsigargin (Tg), that induces store-depletion and 
activates TRPC1-mediated Ca(2+) entry, potentiated the Cl(-) current, which was 
inhibited by the addition of a non-specific TRPC channel blocker SKF96365 or 
removal of external Ca(2+). Stimulation with Tg also increased plasma membrane 
expression of TMEM16a protein, which was also dependent on Ca(2+) entry. 
Importantly, in salivary cells, TRPC1 silencing, but not that of TRPC3, 
inhibited CaCC especially upon store depletion. Moreover, primary acinar cells 
isolated from submandibular gland also showed outward rectifying Cl(-) currents 
upon increasing [Ca(2+)]i. These Cl(-) currents were again potentiated with the 
addition of Tg, but inhibited in the presence of T16Ainh-A01. Finally, acinar 
cells isolated from the submandibular glands of TRPC1 knockout mice showed 
significant inhibition of the outward Cl(-) currents without decreasing TMEM16a 
expression. Together the data suggests that Ca(2+) entry via the TRPC1 channels 
is essential for the activation of CaCC.