When Patch Clamping Won't Work
“Although patch clamping is the standard for measuring ion channels, there are some ion-conducting proteins that it simply cannot be used for,” explained Petr Obrdlik, Ph.D., head of assay development at IonGate Biosciences. “You cannot measure the effects of drugs on the native intracellular organelles because standard patch-clamping equipment cannot access these membranes. I have never seen any publications on patch clamping of respiratory chain complexes and oxidative phosphorylation, for example, so these are valid yet hidden targets for many potential drugs.”
To overcome this problem, IonGate has developed SURFE2R (surface electrogenic event reader) technology that doesn’t use whole cells, but instead, reads the charge displacement from membrane preparations isolated from cell culture. The membranes are coupled via an alkaline thiol and lipid bilayer to gold-coated electrodes, and it is the electrode that detects changes in the electrical signal without the need to use reporter molecules. Beside mitochondrial membranes, the technique is also suited for native membranes from different tissues and different species such as transport proteins of heart plasma membranes, synaptic vesicles, and sarcoplasmic reticulum.
At the “SBS” meeting, an interesting application of the SURFE2R was presented by Victoria Balannik, Ph.D., of Northwestern University. Dr. Balannik showed that, by using the system, it was possible to measure the activity of the anti-influenza drug amantadine on the M2 ion channel protein from influenza A. “It is extremely difficult and time consuming to perform high-throughput screening of the activity of novel anti-viral agents on M2 by conventional electrophysiology,” Dr. Balannik said.
“This technology is complementary to patch clamping,” Stefan Schork, vp of sales at IonGate, concluded. “Since it is now available in a higher throughput format as the SURFE2R Workstation 5000, it will open up the possibility of screening drugs that target transporters and channels in their native sub-cellular surroundings.”