Brain in Flux 2023
When: 12.08. – 15.08.2023
Venue: Vila Nova de Gaia, Portugal.
Go to the Conference website here.
Meet Dr. Andre Bazzone and Rocco Zerlotti
Join Dr. Andre Bazzone (Senior Scientist) and Rocco Zerlotti (Ph.D. student) to learn more about our Solid Supported Membrane (SSM)-based Electrophysiology platforms, SURFE2R N1 and SURFE2R 96SE, that offer sophisticated solutions for the study of membrane transporters, drug discovery, assay development and more.
Nanion will be present with speakers
Andre Bazzone will be present with the talk “Unveiling Transporter Kinetics and Drug Potencies: SGLT1 and TMEM175 in Focus with SSM-based Electrophysiology”
SSM-based electrophysiology (SSME) has emerged as a powerful technique for studying transporters with low turnover rates and intracellular localization, which are challenging to assess using conventional methods. In this talk, we present two recent studies highlighting the capabilities of SSME in functional characterization of transporters and high-throughput drug development.
To investigate the kinetics of sugar binding and translocation, we utilized the Na+/D-glucose co-transporter SGLT1, which holds significant relevance for diabetes treatment. We uncovered a conserved electrogenic conformational transition triggered by sugar binding, providing access to sugar binding kinetics. Through our experiments, we determined rate constants for this transition, unveiling KD values for sugar binding to both the empty carrier and the Na+-bound carrier, as well as KM values for sugar translocation. Utilizing various sugar substrates, we elucidated the kinetic origins of substrate specificity—whether it lies in binding, cooperativity, or translocation. Our findings led us to develop an 11-state kinetic model that describes the observed results.
We also delved into TMEM175, a lysosomal cation channel implicated in Parkinson’s Disease. By investigating lysosomes, we confirmed a PH/PK permeability ratio of 48,500, aligning with existing literature. Next, we established a high-throughput method based on SSME to assess the drug potency of tool compounds. To validate our approach, we compared the results obtained from SSME with those from whole-cell automated patch-clamp, where TMEM175 resides in the plasma membrane, as well as lysosomal patch-clamp. Our comparative analysis revealed that the presence of the lysosomal membrane environment is crucial for accurately estimating drug potencies for TMEM175.
In conclusion, our research raises SSME as a versatile technology capable of efficiently characterizing electrogenic target proteins and facilitating high-throughput drug development. By unlocking the potential of SSME, we gain valuable insights into transporter function and pave the way for the discovery of novel therapeutic interventions.
Rocco Zerlotti will be presenting about “Functional characterization of human GAT-1 through solid supported membrane electrophysiology”
The solid supported membrane-based electrophysiology (SSME) is a technique that allows the measurement of electrogenic events in transporters, pumps, and channels. The sample (i.e., membrane vesicles or proteoliposomes) is adsorbed on an artificial bilayer generated on top of a gold-coated sensor and a capacitive-coupled membrane system is generated. The fluidics of the system allows for a fast solution exchange and transport is triggered by substrate concentration gradients as driving force, while membrane voltage is zero.
GAT-1 is a secondary-active transport protein, abundantly expressed in presynaptic neurons in the CNS. It exploits the Na+ gradient to energize the uphill re-uptake of the neurotransmitter GABA from the synaptic cleft, and it is therefore a therapeutic target for the treatment of neurological disorders linked to GABA homeostasis dysregulation.
Through SSME we detected GABA-induced currents on membrane vesicles overexpressing hGAT-1, with a maximum amplitude of 3-5 nA, that showed a triphasic behavior leading us to identify 3 different electrogenic events. We studied these currents in presence of high and low Na+ gradients, noticing that the middle component disappeared when the Na+ gradient is close to zero. The transport component has been identified, showing a Km of 15-20 μM, and we could also assess the Na+:GABA stoichiometry, which appears to be 2:1.