Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Recombinant dna technique included in method of making a...
Reexamination Certificate
2000-05-04
2003-11-25
Benzion, Gary (Department: 1634)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Recombinant dna technique included in method of making a...
C435S252300, C435S320100, C435S325000, C536S023500
Reexamination Certificate
active
06653100
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of small conductance calcium activated potassium channels, and more specifically to the diagnosis, study, prevention and treatment of disorders related to these channels.
BACKGROUND OF THE INVENTION
Action potentials in vertebrate neurons are followed by an after hyperpolarization (AHP) that may persist for several seconds and may have profound consequences for the neuronal firing pattern. The AHP has several components, which are distinct are mediated by different calcium activated potassium channels. Small conductance calcium activated potassium channels (SKCa, where “S” represents “small”) underlie slow components of the AHP, which are responsible for spike-frequency adaption (Hotson, J. R., and Prince, D. A.,
J. Neurophysiol
. 43:409, 1980). Small conductance channels have a unitary conductance of 4-14ps, are exquisitely sensitive to internal Ca
2+
, lack the property of voltage dependence and are blocked by nanomolar concentrations of the natural toxins apamin and scyllatoxin. These channels modulate the firing pattern of neurons via the generation of slow membrane afterhyperpolarizations (Nicoll, R. A.,
Science
241:545-551, 1988). The intermediate channels (IKCa, where “I” represents intermediate conductance) have a conductance of 11-40 pS, are blocked by charybdotoxin and clotrimazol, and are as sensitive to internal Ca
2+
as SKCa channels (Ishii, T. M., et al.,
Proc. Natl. Acad. Sci. USA
94:11651-11656, 1997; Joiner, W. J., et al.,
Proc. Natl. Acad Sci. USA
94:11013-11018, 1997).
Channel dysregulation, particularly of the glutamate receptor/channels, figures prominently in pathogenic mechanisms involved in many processes leading to neurodegeneration, such as stroke, head trauma, and specific toxic drug reactions. Glutamate is the major excitatory neurotransmitter in the CNS, and while there are five known types of glutamate receptors, the NMDA-type ionotropic receptor/channel complex plays the most prominent role (Sucher, N. J., et al.,
Trends in Pharmacological Sciences
17:348-55, 1996; Kaku, D. A., et al.,
Science
260:1515-8, 1993). Overstimulation of the NMDA pathway produces calcium overload and the excitotoxic death of neurons (Choi, D. W.,
Neuron
1:623-34, 1988). The toxicity may arise through calcium-dependent proteases or through excessive signaling, perhaps leading to apoptosis. Extracellular Mg
2+
produces tonic block of the NMDA receptor/channel complex, and in the presence of its agonist, the receptor/channel conducts an inward sodium and calcium current only if the membrane potential is concurrently being depolarized (Choi, 1988, supra). (This paried input paradigm perhaps also forms an elementary unit in learning, another function subserved by this receptor/channel.) As the cytosolic calcium concentration rises, SKCa channels are activated, generating slow membrane afterhyperpolarizations (Nicoll, R. A.,
Science
241:545-551, 1988; Johnson, S. W., and Seutin, V.,
Neuroscience Letters
231:13-16, 1997). NMDA current is physiologically terminated by this membrane repolarization, which restores the magnesium block. Since SKCa channels regulate ion flow through the NMDA-receptor/channel complex, they play a critical role in dampening neural excitability, and may also contribute to the development of neurological diseases associated with functional alterations in the NMDA signaling pathway (Johnson and Seutin, 1997, supra).
The SKCa are currents that have been described in a wide range of tissues, including brain (Lancaster, B. and Nicoll, R. A.,
J. Physiol
. 389:187-203, 1987), peripheral neurons (Goh, J. W., and Pennefather, P. S.,
J. Physiol
. 394:315-330,1987), skeletal muscle (Romey, G., and Lazdunski, M.,
Biochem. Biophys. Res. Commun
. 118:669-674, 1984) adrenal chromaffin cells (Neely, A., and Lingle, C. J.,
J. Physiol
. 452:97-131, 1992), leukocytes (Grissmer, S., et al.,
J. Gen. Physiol.
99:63-84, 1992), erythrocytes (Hamill, O. P.,
J. Physiol
. 319:97P-98P, 1981), colon (Lomax, R. B., et al.,
Gut
38:243-247, 1996), and airway epithelia (Welsh, M. J., and McCann, J. D.,
Proc. Natl. Acad. Sci. USA
82:8823-8826, 1985). Certain types of SKCa channels have been distinguished by their sensitivities to the bee venom apamin, whereas other functionally related conductances appear insensitive (Sah, P., and AcLachlan, E. M., 1992
, J. Neurophysiol
. 74:1772-1776). The distinguishing features of the SKCa channels from the maxi-K calcium activated (BK) potassium channels are the SKCa channels' low conductance (less than 50 pS), the weak or negligible dependence of their activity on membrane voltage, and their high affinity for calcium (EC
50
<1 &mgr;M) (e.g., Lancaster, B., and Zucker, R. S.,
J. Physiol
. 475:229-239, 1994).
Recently, Imbert et al. reported the cloning of six novel cDNAs, each containing one or more long CAG repeats. These cDNAs were isolated from a lymphoblastoid cell cDNA expression library generated from patients with autosomal dominant cerebellar ataxia with a monoclonal antibody specific for polyglutamine sequences (Imbert et al.,
Nature Genetics
14:285, 1996). One of the cDNAs, designated AAD14, encoded the partial sequence of a putative protein of 228 amino acids in length. This polypeptide of unknown function contained two long polyglutamine stretches.
Kohler et al. first described a rat small conductance calcium activated potassium channel (rSKCa3) gene, and published the truncated form of the gene (Kohler et al.,
Science
274:1709, 1996). An alignment of the known members of the small conductance calcium-activated potassium channels was described by Joiner et al. (
Proc. Natl. Acad Sci
. 94:11013, 1997), who cloned the hSK4 gene, using the potassium channel signature sequence (TXXTXGYG, SEQ ID NO:9). Ishii et al. (
Proc. Natl. Acad. Sci. USA
94:11651-6, 1997) further cloned an intermediate conductance calcium-activated potassium channel (h1K1).
Schizophrenia is a chronic disabling disorder with a lifetime morbid risk of 1% in the general population. The illness has a significant genetic component (Kendler, K. S., In:
Relatives at Risk for Mental Disorders
, Dunner, D. L., Gershon, E. S., and Barrett, J. E. (eds), Raven Press, New York, pp. 247-263, 1988) and often develops in early adulthood. The disease is characterized by a constellation of symptoms including hallucinations and delusions, disordered thinking and concentration, inappropriate emotional responses, catatonia, erratic behavior, and social and occupational deterioration. Although still controversial, “anticipation” (an increase in severity through successive generations) has been found in studies of affected families (Bassett, A. S., and Honer, W. G.,
Am. J. Hum. Genet
., 54:864-870, 1994). Trinucleotide repeat expansions have been found to underlie several Mendelian hereditary neurological diseases (Ashley, C. T., Jr., and Warren, S. T.,
Annu. Rev. Genet
., 29:703-728, 1995; Timchenko, L. T., and Caskey, C. T.,
FASEB J
., 10:1589-1597, 1996; among others).
Several human hereditary neurological diseases, such as Huntington's disease, fragile X syndrome, myotonic dystrophy, spinal and bulbar muscular atrophy, Machado-Joseph disease, Friedrich's disease and spinocerebellar ataxia, are associated with expanded trinucleotide repeats (typically>35) within the coding region (e.g., Timchenko, L. T., and Caskey, C. T.,
FASEB J
. 10:1589-97,1996; Hannan, A. J.,
J. Clin. Exp. Pharm. Physiol
. 23:1015-20, 1996; Bates, G.,
Bioessays
18:1 75-8, 1996), untranslated sequences (e.g., Warren, S. T., and Ashley, C. T.,
Ann. Rev. Neurosci
. 18:77-99, 1995; Tsilfidis, C., et al.,
Nature Genet
. 1:192-195, 1992), or introns (Campuzano, V., et al.,
Science
271:1423-7, 1996) of genes. An association has been shown between the presence of anonymous CAG/CTG repeats and the development of schizophrenia and bipolar disease (O'Donovan, M. C., et al.,
Nature Genetics
10:380-1, 1995; O'Donovan et al.,
Psychological Med
. 26:1145-1153, 1996;
Chandy K. George
Fantino Emmanuelle
Gargus J. Jay
Gutman George
Kalman Katarin
Benzion Gary
Chakrabarti Arun Kr.
Gray Cary Ware & Freidenrich LLP
The Regents of the University of California
LandOfFree
hKCa3/KCNN3 small conductance calcium activated potassium... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with hKCa3/KCNN3 small conductance calcium activated potassium..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and hKCa3/KCNN3 small conductance calcium activated potassium... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3125038