Abstract
Na+/H+ exchanger 3 (NHE3) plays a pivotal role in transepithelial Na+ and HCO3(-) absorption across a wide range of epithelia in the digestive and renal-genitourinary systems. Accumulating evidence suggests that PDZ-based adaptor proteins play an important role in regulating the trafficking and activity of NHE3. A search for NHE3-binding modular proteins using yeast two-hybrid assays led us to the PDZ-based adaptor Shank2. The interaction between Shank2 and NHE3 was further confirmed by immunoprecipitation and surface plasmon resonance studies. When expressed in PS120/NHE3 cells, Shank2 increased the membrane expression and basal activity of NHE3 and attenuated the cAMP-dependent inhibition of NHE3 activity. Furthermore, knock-down of native Shank2 expression in Caco-2 epithelial cells by RNA interference decreased NHE3 protein expression as well as activity but amplified the inhibitory effect of cAMP on NHE3. These results indicate that Shank2 is a novel NHE3 interacting protein that is involved in the fine regulation of transepithelial salt and water transport through affecting NHE3 expression and activity.
Highlights
Na؉/H؉ exchanger 3 (NHE3) is known to be regulated by a large variety of hormones, such as ␣- and -adrenergic agonists, dopamine, parathyroid hormone, and angiotensin II via multiple signaling systems [6, 7], but the exact underlying mechanisms are still only partially understood
It has been demonstrated that adaptor proteins with PDZ (PSD-95/discs large/ ZO-1) domains play an important role in the cAMP-dependent inhibition of NHE3 in a number of systems [7, 9, 10]
Knock-down of native Shank2 expression by RNA interference evoked a remarkable decrease in endogenous NHE3 activity in Caco-2 colonic epithelial cells
Summary
NHE3 is known to be regulated by a large variety of hormones, such as ␣- and -adrenergic agonists, dopamine, parathyroid hormone, and angiotensin II via multiple signaling systems [6, 7], but the exact underlying mechanisms are still only partially understood. Knock-down of native Shank2 expression by RNA interference evoked a remarkable decrease in endogenous NHE3 activity in Caco-2 colonic epithelial cells.
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