| First Author | Dickerson MT | Year | 2017 |
| Journal | PLoS One | Volume | 12 |
| Issue | 4 | Pages | e0175069 |
| PubMed ID | 28403169 | Mgi Jnum | J:248113 |
| Mgi Id | MGI:5918602 | Doi | 10.1371/journal.pone.0175069 |
| Citation | Dickerson MT, et al. (2017) Osteopontin activates the diabetes-associated potassium channel TALK-1 in pancreatic beta-cells. PLoS One 12(4):e0175069 |
| abstractText | Glucose-stimulated insulin secretion (GSIS) relies on beta-cell Ca2+ influx, which is modulated by the two-pore-domain K+ (K2P) channel, TALK-1. A gain-of-function polymorphism in KCNK16, the gene encoding TALK-1, increases risk for developing type-2 diabetes. While TALK-1 serves an important role in modulating GSIS, the regulatory mechanism(s) that control beta-cell TALK-1 channels are unknown. Therefore, we employed a membrane-specific yeast two-hybrid (MYTH) assay to identify TALK-1-interacting proteins in human islets, which will assist in determining signaling modalities that modulate TALK-1 function. Twenty-one proteins from a human islet cDNA library interacted with TALK-1. Some of these interactions increased TALK-1 activity, including intracellular osteopontin (iOPN). Intracellular OPN is highly expressed in beta-cells and is upregulated under pre-diabetic conditions to help maintain normal beta-cell function; however, the functional role of iOPN in beta-cells is poorly understood. We found that iOPN colocalized with TALK-1 in pancreatic sections and coimmunoprecipitated with human islet TALK-1 channels. As human beta-cells express two K+ channel-forming variants of TALK-1, regulation of these TALK-1 variants by iOPN was assessed. At physiological voltages iOPN activated TALK-1 transcript variant 3 channels but not TALK-1 transcript variant 2 channels. Activation of TALK-1 channels by iOPN also hyperpolarized resting membrane potential (Vm) in HEK293 cells and in primary mouse beta-cells. Intracellular OPN was also knocked down in beta-cells to test its effect on beta-cell TALK-1 channel activity. Reducing beta-cell iOPN significantly decreased TALK-1 K+ currents and increased glucose-stimulated Ca2+ influx. Importantly, iOPN did not affect the function of other K2P channels or alter Ca2+ influx into TALK-1 deficient beta-cells. These results reveal the first protein interactions with the TALK-1 channel and found that an interaction with iOPN increased beta-cell TALK-1 K+ currents. The TALK-1/iOPN complex caused Vm hyperpolarization and reduced beta-cell glucose-stimulated Ca2+ influx, which is predicted to inhibit GSIS. |
