No abstract

The sodium leak channel (NALCN) is essential for survival in mammals: NALCN mutations are life-threatening in humans and knockout is lethal in mice. However, the basic functional and pharmacological properties of NALCN have remained elusive. Here, we found that robust function of NALCN in heterologous systems requires co-expression of UNC79, UNC80, and FAM155A. The resulting NALCN channel complex is constitutively active and conducts monovalent cations but is blocked by physiological concentrations of extracellular divalent cations. Our data support the notion that NALCN is directly responsible for the increased excitability observed in a variety of neurons in reduced extracellular Ca2+. Despite the smaller number of voltage-sensing residues in NALCN, the constitutive activity is modulated by voltage, suggesting that voltage-sensing domains can give rise to a broader range of gating phenotypes than previously anticipated. Our work points toward formerly unknown contributions of NALCN to neuronal excitability and opens avenues for pharmacological targeting.

No abstract

AbstractManipulation of proteins by chemical modification is a powerful way to decipher their function or harness that function for therapeutic purposes. Despite recent progress in ribosome-dependent and semi-synthetic chemical modifications, these techniques sometimes have limitations in the number and type of modifications that can be simultaneously introduced or their application in live eukaryotic cells. Here we present a new approach to incorporate single or multiple post-translational modifications or non-canonical amino acids into soluble and membrane proteins expressed in eukaryotic cells. We insert synthetic peptides into proteins of interest via tandem protein trans-splicing using two orthogonal split intein pairs and validate our approach by investigating different aspects of GFP, NaV1.5 and P2X2 receptor function. Because the approach can introduce virtually any chemical modification into both intracellular and extracellular regions of target proteins, we anticipate that it will overcome some of the drawbacks of other semi-synthetic or ribosome-dependent methods to engineer proteins.

Manipulation of proteins by chemical modification is a powerful way to decipher their function. However, most ribosome-dependent and semi-synthetic methods have limitations in the number and type of modifications that can be introduced, especially in live cells. Here, we present an approach to incorporate single or multiple post-translational modifications or non-canonical amino acids into proteins expressed in eukaryotic cells. We insert synthetic peptides into GFP, Na V 1.5 and P2X2 receptors via tandem protein trans-splicing using two orthogonal split intein pairs and validate our approach by investigating protein function. We anticipate the approach will overcome some drawbacks of existing protein enigineering methods.