RESEARCH INTEREST

Molecular mechanisms of regulation of neuronal excitability; modulation of neuronal ion channels.


RESEARCH TECHNIQUES

Molecular, biochemical and biophysical characterization of ion channels and associated signaling proteins; antibody generation and characterization; co-immunoprecipitation; molecular cloning and mutagenesis; mammalian cell culture; bacterial and mammalian cell expression; yeast two-hybrid screens; patch clamp and voltage clamp analysis of ion channel activity in neurons and heterologous cells; Drosophila genetics, electrophysiology and behavior.


RESEARCH SUMMARY

My laboratory is interested in the long term regulation of neuronal excitability and synaptic transmission. We study the molecular mechanisms that nerve cells use to modulate the activity of individual ion channels, since these mechanisms must contribute to long term changes in neuronal function and ultimately in behavior. The essence of our approach is a combination of biochemistry, molecular biology, genetics and electrophysiology, at the level of individual neurons, synapses and ion channels. We study the electrophysiological properties of native channels in neurons, and of cloned channels expressed in heterologous host cells, using patch recording techniques. In parallel we carry out biochemical measurements of channel proteins, making use of specific antibodies directed against channel epitopes. One theme that we are pursuing vigorously is the idea that channels do not exist on their own in the plasma membrane, but rather are part of a regulatory complex that includes signaling proteins that are involved in the modulation of channel function. For example, we have found that the Src tyrosine kinase, the catalytic subunit of cyclic AMP-dependent protein kinase and the ubiquitous calcium sensor calmodulin all bind directly to potassium channels and influence their function. We also have isolated a novel protein named Slob, which binds to and modulates the Slowpoke calcium-dependent potassium channel. We are investigating the molecular details and physiological significance of the dynamic interactions of Slob, the protein kinases, calmodulin and other signaling proteins with several different kinds of potassium channels. One way we do this is by using genetics to introduce mutant channels and their binding partners into flies and ask questions about the roles of ion channel regulatory complexes in neuronal physiology and behavior.

KEY REFERENCES

Tian, L., Duncan, R.R., Hammond, M., Coghill, L.S., Wen, H., Rusinova, R., Clark, A.G., Levitan, I.B. and Shipston, M.J. J. Biol. Chem. 276, 7717-7720 (2001) Alternative splicing switches potassium channel sensitivity to protein phosphorylation.

Levitan, I.B. and Cibulsky, S.M. Science 293, 1270-1271 (2001) TRP Ion channels-two proteins in one.

Levitan, I.B. and MacFarlane, S.N. Science's STKE, 1/98/pe1 (2001) Unzipping ion channels. Online PDF File

Weiger, T.M., Hermann, A. and Levitan, I.B. J. Comp. Physiol. 188, 79-87 (2002) Modulation of calcium activated potassium channels.

Jin, P., Weiger, T.M., Wu, Y. and Levitan, I.B. J. Biol. Chem. 277, 10014-10020 (2002) Phosphorylation-dependent functional coupling of hSlo calcium-dependent potassium channel and its hbeta4 subunit.

Zhou, Y., Wang, J., Wen, H., Kucherovsky, O. and Levitan, I.B. J. Neurosci. 22, 3855-3863 (2002) Modulation of Drosophila slowpoke calcium-dependent potassium channel activity by bound protein kinase A catalytic subunit.

Wen, H. and Levitan, I.B. J. Neurosci. 22, 7991-8001 (2002) Calmodulin is an auxiliary subunit of KCNQ2/3 potassium channels.

Jin, P., Weiger, T.M. and Levitan, I.B. J. Biol. Chem. 277, 43724-43729 (2002) Reciprocal modulation between the alpha and beta subunits of hSlo calcium-dependent potassium channels.

Zhou, Y., Reddy, S., Murrey, H., Fei, H. and Levitan, I.B. J. Biol. Chem. 278(12), 10073-10080 (2003) Monomeric 14-3-3 protein is sufficient to modulate the activity of the Drosophila slowpoke calcium-dependent potassium channel.

Jaramillo, A.M., Zheng, X., Zhou, Y., Amado, D.A., Sheldon, A., Sehgal, A. and Levitan, I.B. BMC Neurosci. 5: 3 (2004) Pattern of distribution and cycling of SLOB, slowpoke channel binding protein, in Drosophila.Online PDF File

Levitan, I.B. Science 304: 394-395 (2004) Cell biology. A well-stocked pool. Online PDF File

Zeng, H., Fei, H. and Levitan, I.B. Neuroscience Letters, 365: 33-38 (2004) The slowpoke channel binding protein Slob from Drosophila melanogaster exhibits regulatable protein kinase activity. Online PDF File

Cibulsky, S, Fei, H. and Levitan, I.B. J. Neurophysiol. 93:1393-1405 (2005) Syntaxin-1A binds to and modulates the Slo calcium-activated potassium channel. Online PDF File

Zeng, H., Weiger, M., Fei, H., Jaramillo, A. and Levitan, I.B. J. Gen. Physiol. 125:631-640 (2005) The amino terminus of Slob, Slowpoke channel binding protein, critically influences its modulation of the channel.Online PDF File

Mao, H., Ferguson , T.S., Cibulsky, S.M., Holmqvist, M., Ding, C., Fei, H. and Levitan, I.B. J. Neurosci. 25(35):7934-7943 (2005) MONaKA, a novel modulator of the plasma membrane Na,K-ATPase. Online PDF File

Wen, H., Weiger, T.M., Ferguson, T.S., Shahidullah, M., Scott, S.S. and Levitan, I.B. J. Neurosci. 25:10147-10156 (2005) A Drosophila KCNQ channel essential for early embryonic development. Online PDF File 

Shahidullah, M., Santarelli, L.C., Wen, H. and Levitan, I.B. PNAS 102:16454-16459 (2005) Expression of a calmodulin-binding KCNQ2 potassium channel fragment modulates neuronal M-current and membrane excitability. Online PDF File

Levitan, I.B. Nature Neuroscience 9:305-310 (2006) Signaling protein complexes associated with neuronal ion channels. Online PDF File

Jaramillo, A., Zeng, H., Fei, H., Zhou, Y., and Levitan, I.B. J. Neurophysiol. 95:1957-1965 (2006) Expression and function of varients of Slob, Slowpoke channel bindingprotein, in Drosophila. Online PDF File

Zeng, H., Weiger, T.M., Fei, H., and Levitan, I.B. J. Gen. Physiol. Vol. 128: 583-591, (2006) Mechanisms of two modulatory actions of the channel-binding protein Slob on the Drosophila Slowpoke calcium-dependent potassium channel. . Online PDF File