Baron Chanda, Ph.D. Assistant Professor Department of Physiology bchanda@physiology.wisc.edu

Research Interests: Structural mechanisms underlying voltage-dependent gating in ion channels

The objective of my research is to understand how structure and dynamics determine the function of the voltage-dependent ion channels. In response to a change in membrane potential, voltage-dependent ion channels undergo a series of conformational changes culminating in the opening or closing of the channel. We use a variety of biophysical methods to track the structural changes that of these processes. Electrophysiological methods like ionic and “gating” current measurements provide information about the global structural changes. Site-specific fluorescence recordings and cysteine accessibility methods, on the other hand, provide information about the local structural changes in the protein. These methods complement one another and together they provide a detailed physical model of the workings of an ion channel.
 
We are currently focusing on understanding how the voltage-dependent gating behavior of sodium channels is modified by gating-modifier toxins and local anesthetics. Sodium channel malfunction has been associated with disease conditions like cardiac arrhythmias and epilepsies. Local anesthetics alleviate these disease states by reducing electrical excitability of the sodium channels. We are using voltage-clamp fluorimetry to map the structural changes in the sodium channels induced by local anesthetics. These studies are expected to provide fundamental insights into the physical mechanisms of gating and modulation of the Na+ channel.

Another area of interest in the lab is to understand how temperature modulates voltage-dependent gating of TRP ion channels. Some members of the TRP family respond acutely either to a heat or to a cold stimulus. Recently, it has been shown that these channels are also voltage-dependent and that temperature affects their voltage-dependent gating. We are interested in understanding the biophysical principles that govern temperature dependent gating of these channels using both time-resolved spectroscopic as well as electrophysiological approaches.

Selected Publications: Articles on PubMed

• Campos F, Chanda B, Baeiro P, and Bezanilla F. (2008). α-scorpion toxin impairs a conformational change that leads to fast inactivation of the sodium channels. J Gen Physiol. 132:251-263.
  
  
• Chanda B and Bezanilla F. (2008). A common pathway for charge transport through voltage-sensing domains. Neuron. 57:345-351.

• Campos FV, Chanda B, Beirao PS, Bezanilla F. (2007). b-Scorpion Toxin Modifies Gating Transitions in All Four Voltage Sensors of the Sodium Channel. J Gen Physiol. 130:257-268. PMID 17698594
  
  
• Campos FV, Chanda B, Roux B, Bezanilla F. (2007). Two atomic constraints unambiguously position the S4 segment relative to S1 and S2 segments in the closed state of Shaker K channel. Proc Natl Acad Sci U S A. 104:7904-7909. PMID 17470814
  
  
• Ben-Chaim Y, Chanda B, Bezanilla F, Dascal N, Parnas I, and Parnas H. (2006). Movement of “gating charge” is coupled to ligand binding in a G-protein coupled receptor. Nature. 444:106-109. PDF PMID 17065983
   
  
• Bannister JP, Chanda B, Bezanilla F, and Papazian DM. (2005). Optical detection of rate-determining, ion-modulated conformational changes of the ether-à-go-go K+ channel voltage sensor. PNAS USA. 102:18718-19723. PDF PMID 16339906
   
  
• Chanda B, Blunck R, Faria LC, Schweizer FE, Mody I, and Bezanilla F. (2005). A hybrid approach to measuring electrical activity in genetically specified neurons. Nature Neurosci. 8:1619-1626. PMID 16205716
   
  
• Chanda B, Asamoah OK, Blunck R, Roux B, and Bezanilla F. (2005). Gating charge displacement in voltage-gated ion channels involves limited transmembrane movement. Nature. 436:852-836. PDF PMID 16094369
   
  
• Chanda B, Asamoah OK, and Bezanilla F. (2004). Coupling interactions between voltage sensors of the sodium channel as revealed by site-specific measurements. J Gen Physiol. 123:217-230. PDF PMID 14981134
   
  
• Chanda B and Bezanilla F. (2002). Tracking voltage-dependent conformational changes in skeletal muscle sodium channel during activation. J Gen Physiol. 120:629-645. PDF PMID 12407076