Regulation of GIP and GLP1 receptor cell surface expression by N-glycosylation and receptor heteromerization.

In response to a meal, Glucose-dependent Insulinotropic Polypeptide (GIP) and Glucagon-like Peptide-1 (GLP-1) are released from gut endocrine cells into the circulation and interact with their cognate G-protein coupled receptors (GPCRs). Receptor activation results in tissue-selective pleiotropic responses that include augmentation of glucose-induced insulin secretion from pancreatic beta cells. N-glycosylation and receptor oligomerization are co-translational processes that are thought to regulate the exit of functional GPCRs from the ER and their maintenance at the plasma membrane.

Using Bioluminescence Resonance Energy Transfer to measure ion channel assembly.

Bioluminescence Resonance Energy Transfer (BRET) measures protein interactions within 10 nm of each other. Aside from its ability to probe for interactions at high resolution, this technique operates in live, intact cells, and offers a high throughput method of detection. Thus far, BRET has been widely used in measuring G protein receptor dimerization.

Hyperpolarization-activated cyclic nucleotide-modulated 'HCN' channels confer regular and faster rhythmicity to beating mouse embryonic stem cells.

The hyperpolarization-activated cation current (I(f)), and the hyperpolarization-activated cyclic nucleotide-modulated 'HCN' subunits that underlie it, are important components of spontaneous activity in the embryonic mouse heart, but whether they contribute to this activity in mouse embryonic stem cell-derived cardiomyocytes has not been investigated. We address this issue in spontaneously beating cells derived from mouse embryonic stem cells (mESCs) over the course of development in culture. I(f) and action potentials were recorded from single beating cells at early, intermediate and late development stages using perforated whole-cell voltage- and current-clamp techniques.

HCN2 and HCN4 isoforms self-assemble and co-assemble with equal preference to form functional pacemaker channels.

Hyperpolarization-activated cyclic nucleotide-modulated (HCN) "pacemaker" channel subunits are integral membrane proteins that assemble as tetramers to form channels in cardiac conduction tissue and nerve cells. Previous studies have suggested that the HCN2 and HCN4 channel isoforms physically interact when overexpressed in mammalian cells, but whether they are able to co-assemble and form functional channels remains unclear. The extent to which co-assembly occurs over self-assembly and whether HCN2-HCN4 heteromeric channels are formed in native tissue are not known.