News and Publications

Neuropeptides and Sleep

L. de Lecea, J.G. Sutcliffe, J.R. Criado, M. Calbet

We recently used recombinant methods to isolate cortistatin-14, a novel neuropeptide that shares 11 of its 14 residues with somatostatin-14. Preprocortistatin is expressed in a distinct subset of cortical and hippocampal inhibitory neurons (Fig. 1). The effects of cortistatin on sleep physiology, locomotor behavior, and hippocampal function differ from those of somatostatin. We have studied the structural basis for cortistatin's distinct biological activities.

Like somatostatin, cortistatin-14 does not show any preferred conformation in solution, as determined by circular dichroism and nuclear magnetic resonance. We designed and synthesized cortistatin analogs based on the cyclic structure of sandostatin, a potent somatostatin analog. Biological assays were done to determine the binding affinities of the analogs to 5 somatostatin receptors and the ability of the synthesized compounds to produce changes in locomotor activity and to modulate hippocampal physiology and sleep. Compounds with N-terminal proline and C-terminal lysine amide had cortistatin-like biological activities, including reduction of population spike amplitudes in the hippocampal CA1 region, decrease in locomotor activity, and enhancement of slow-wave sleep and bound selectively to somatostatin receptor 3.

Our findings suggest that both proline and lysine are necessary for the binding of cortistatin to its specific receptor. The peptide Pro-c[Cys-Tyr-d-Trp-Lys-Val-Cys]-Lys-NH₂ discovered in our studies is the first synthetic analog of cortistatin and provides a useful reagent to investigate the selective effects of cortistatin on cortical activity and states of arousal.

To investigate the effects of cortistatin in vivo, we generated transgenic mice that express preprocorti-statin under the control of the neuron-specific enolase promoter. Initial characterization of these transgenic mice revealed strong synaptic depression in the dentate gyrus. Our data suggest that cortistatin is an inhibitory peptide that modulates hippocampal synaptic activity in vivo.

PUBLICATIONS

Alcántara, S., Ruiz, M., D'Arcangelo, G., Ezan, F., de Lecea, L., Curran, T., Sotelo, C., Soriano, E. Regional and cellular patterns of reelin mRNA expression in the forebrain of the developing and adult mouse. Eur. J. Neurosci., in press.

de Lecea, L., Criado, J.R., Rivera, S., Wen, W., Soriano, E, Henriksen, S.J., Taylor, S.S., Gall, C.M., Sutcliffe, J.G. Endogenous protein kinase A inhibitor (PKI/alphapub/) modulates synaptic activity. J. Neurosci. Res., in press.

de Lecea, L., Kilduff, T., Peyron, C., Gao, X.B., Fukuhara, C., Danielson, P.E., Foye, P.E., Bartlett, F.S. II, Gautvik, V.T., van den Pol, A.N., Frankel, W.N., Bloom, F.E., Gautvik, K.M., Sutcliffe, J.G. The hypocretins: Two hypothalamic peptides with neuroexcitatory activity. Proc. Natl. Acad. Sci. U.S.A. 95:322, 1998.

Kilduff, T., de Lecea, L., Usui, H., Sutcliffe, J.G. Isolation and identification of specific transcripts by subtractive hybridization. In: Molecular Regulation of Conscious States. Lydic, R. (Ed.). CRC Press, Boca Raton, FL, 1997, p. 103.

Rocamora, N., Pascual, M., Acsady, L., de Lecea, L., Freund, T.F., Soriano, E. A triple labeling method combining in situ hybridization for neurotrophins, immunohistochemistry for neuronal markers and anterograde tracing with Phaseolus vulgaris leucoagglutinin. J. Histochem. Cytochem., in press.