Biology subjects

Estrada-Mondragon, A.

Publications and source records attributed to Estrada-Mondragon, A..

3 recordsLinked to original sources

bioRxiv2020

Multiple binding sites for resin-acid derivatives on the voltage-sensor domain of the Shaker potassium channel

Voltage-gated potassium (KV) channels can be opened by negatively charged resin acids and their derivatives. These resin acids have been proposed to attract the positively charged voltage-sensor helix (S4) toward the extracellular side of the membrane by binding to a pocket located between the lipid-facing extracellular ends of the transmembrane segments S3 and S4. By contrast to this proposed mechanism, neutralization of the top gating charge of the Shaker KV channel increased resin-acid induced opening, suggesting other mechanisms and sites of action. Here we explored the binding of two resin-acid derivatives, Wu50 and Wu161, to the activated/open state of the Shaker KV channel by a combination of in-silico docking, molecular dynamics simulations, and electrophysiology of mutated channels. We identified three potential resin-acid binding sites around S4: (1) The S3/S4 site previously suggested, in which positively charged residues introduced at the top of S4 are critical to keep the compound bound, (2) a site in the cleft between S4 and the pore domain (S4/pore site), in which a tryptophan at the top of S6 and the top gating charge of S4 keeps the compound bound, and (3) a site located on the extracellular side of the voltage-sensor domain, in a cleft formed by S1-S4 (the top-VSD site). The multiple binding sites around S4 and the anticipated helical-screw motion of the helix during activation make the effect of resin-acid derivatives on channel function intricate. The propensity of a specific resin acid to activate and open a voltage-gated channel likely depends on its exact binding dynamics and the types of interactions it can form with the protein in a state-specific manner. eTOC SummarySilver[a] Ejneby et al use molecular dynamics simulations and electrophysiology to show that the voltage-gated Shaker potassium channel has multiple binding sites for resin-acid derivatives that can regulate its opening.

biophysics↗

bioRxiv2020

A phylogenetic analysis of MCTP proteins: from amino acid sequence to function

MCTPs (Multiple C2 domain proteins with two transmembrane regions) are evolutionarily and structurally related to other C2 proteins which play fundamental roles in exocytosis and membrane trafficking, however their specific role has been little studied. This work points out possible functional implications of MCTPs by comparing their primary amino acid sequence and functional domains. MCTP amino acid sequences were identified in non-chordates and chordates. The primary sequences grouped in three classes: MCTP, MCTP-1 and MCTP-2. MCTP is present only in non-chordates, while MCTP-1 and MCTP-2 are present in chordates. MCTP genes emerged early in metazoan evolution and are well conserved across species including humans. Genomic analysis of diverse species of representative phyla showed that the three C2 domains (C2A-C2C) and transmembrane regions (TMR) are well conserved. The C2 domains have eight {beta} strands as well as aspartate residues known to bind calcium. Interestingly, we identified a lysine-rich cluster, also known as polybasic cluster in C2A and C2B, which is known to bind lipids in other proteins. We also describe the phylogenetic distribution of MCTPs and analyze conserved domains and their predicted secondary structure in metazoans. We highlight important motifs that have not been previously described in MCTPs C2A and C2B domains that suggest MCTPs potentially bind phospholipids. Our observations show MCTPs are proteins widely distributed in eukaryotic organisms and may play an important role in membrane fusion or exocytosis.

cell biology↗

bioRxiv2018

Phosphorylation of the alpha2 glycine receptor induces an extracellular conformational change and slows the rise and decay rates of glycinergic synaptic currents

The 2 glycine receptor (GlyR) is a pentameric ligand-gated anion channel that plays a key role in cortical interneuron migration and in the differentiation of cortical progenitor cells into functional neurons. It also mediates tonic inhibitory chloride currents in adult forebrain neurons. Disruption of 2 GlyR gene expression or receptor function results in the aberrant functioning of neuronal circuits which contributes to the pathophysiology of schizophrenia, autism and epilepsy. This implicates the 2 GlyR as a possible therapeutic target for a range of neurological disorders. However, despite its therapeutic potential, little is known about the mechanisms by which 2 GlyRs are functionally modulated. To address this, we investigated whether the 2 GlyR is modulated by phosphorylation at a serine residue (S341) within the same PKA consensus sequence (R-E-S-R) that houses the 3 GlyR S346 residue that is known to be phosphorylated by PKA. Resolving this question might uncover a novel means of physiologically, pathologically or therapeutically modulating 2 GlyRs. We show using voltage-clamp fluorometry that forskolin-induced phosphorylation of S341 induces a conformational change in the glycine binding site. We also employed glycinergic artificial synapses to demonstrate that the S341E phospho-mimetic mutation slows the rise and decay rates of 2-mediated glycinergic inhibitory postsynaptic currents. These results suggest that PKA phosphorylation alters the structural and functional properties of the 2 GlyR. This information may help to identify new mechanisms by which 2 GlyRs may be pathologically modified or therapeutically targeted for the treatment of neurological disorders.

neuroscience↗