Scientific Report 2003-2004 - Cleveland Clinic Lerner Research ...

Our laboratory investigates the structurefunctionand physiological action of α 1-adrenergic receptors (α 1-ARs). Theseseven-transmembrane-spanning proteins belong tothe G-protein-coupled receptor superfamily,through which over 80% of all hormones signaland carry out their physiological functions. ARsmodulate the sympathetic nervous system bybinding epinephrine and norepinephrine andcontrol cardiovascular functions such as bloodpressure homeostasis and cardiac contractility.Three subtypes of the α 1-AR family (α 1A, α 1B, andα 1D) derive from separate gene products and bindseveral synthetic agonists and antagonists withdifferent affinities. We study the amino acidsinvolved in this ligand selectivity between ARsubtypes, seeking to develop better therapeutics(Waugh et al., J. Biol. Chem., 2001). We do notyet know which α 1-AR subtypes control thevarious physiologies attributed to these receptors,whether the subtypes differ physiologically, orwhether abnormalities in their function lead todisease. To this end, we recently performedmicroarray studies in transfected cells expressingindividual α 1-AR subtypes and found that theycan couple to interleukin-6, JAK/STAT, and cellcycleregulation pathways (Gonzalez-Cabrera etal., Mol. Pharmacol., 2003). Ongoing experimentswith transgenic mice that systemically overexpressα 1-AR subtypes are addressing these questions.Overexpression of the α 1B-AR receptorcauses neurodegeneration consistent withmultiple system atrophy (MSA), a parkinsoniansyndrome (Zuscik et al., Nat. Med., 2000).Afflicted patients die within 9 years of diagnosis,and no effective treatment is available. As inhuman disease, our mice show major degenerationin the cerebellum, olive/pons, and spinal cord.The mice exhibit parkinsonian traits, since there istyrosine hydroxylase loss in the substantia nigra.They have autonomic failure, a characteristic ofMSA (i.e., low plasma levels of catecholamines,cortisol, ACTH and corticotropin-releasing factor,low blood pressure, bradycardia, reproductiveproblems, and weight loss) (Zuscik et al., J. Biol.Chem., 2001). Cytoplasmic inclusion bodies fromthese mice stain positive for α-synuclein andubiquitin in oligodendrocytes, a hallmark of MSA(Papay et al., J. Neurochem., 2002). In this model,α 1-AR blockers can partially rescue thedegradative phenotype (i.e., improve motorperformance). In work with CCF’s Departmentof Neurology, clinical trials are testing whetherα 1-AR blockers benefit MSA patients. We alsoplan studies to find the molecular basis for thisneurodegeneration, which may occur through anThe Department of Molecular CardiologyMouse Models of α 1-Adrenergic ReceptorOverexpression Offer Insights intoNeurodegeneration, Epilepsy,and Heart Disordersapoptotic mechanism (Yun et al., Brain, 2003) orthrough abnormal forms of α-synuclein (Papay etal., J. Neurochem., 2002).Interestingly, the α 1B-AR transgenic miceare epileptic. With our Neurology colleagues, wehave shown that these mice show abnormal waveforms by EEG (Kunieda et al., Epilepsia, 2002).Associated with the age onset of seizures, certainNMDA receptor subunits are upregulated andGABA receptors downregulated; both are criticalto maintaining the brain’s balance of excitatory/inhibitory signals. Understanding how seizures areinduced may provide clues to the onset ortreatment of human epilepsy.These transgenic mice show many cardiovascularabnormalities. Cardiac hypertrophy(enlargement of the heart) can sometimesprogress to heart failure. Understanding theinduction and progression of cardiac hypertrophyis crucial to preventing heart failure. Using genechip microarray analysis on transgenic hearts, wehave investigated the changes in gene expressionthat occur as hypertrophy caused by overexpressionof the α 1B-AR progresses (Yun et al.,Cardiovasc. Res., 2003). Notably, in young mice,we saw early events of apoptosis and changes intyrosine kinase signaling, whereas older micedisplayed genes associated with embryogenesisand inflammation, suggesting that an etiology ofapoptosis and Src-related signaling may be crucialto initiating hypertrophy. Induction of hypertrophy-associatedgenes, such as gp130, wasdownregulated in transgenic hearts. Loss ofgp130 has been associated with the transition toheart failure. We are exploring the α 1B-AR’s rolein modulating cardiac contractility and rhythm.THE D. PEREZLABORATORYPOSTDOCTORAL FELLOWSPedro Gonzalez-Cabrera, Ph.D.Dan McCune, Ph.D.Boyd Rorabaugh, Ph.D.June Yun, Ph.D.TECHNICAL ASSOCIATESRobert Gaivin, B.A.Robert Papay, B.S.COLLABORATORSWarren (Skip) Heston, Ph.D. 1Wendy Macklin, Ph.D. 2Imad Najm, M.D. 3Michael T. Piascik, Ph.D. 4Thyagarajan Subramanian, M.D. 3James Thomas, M.D. 51Dept. of Cancer Biology, CCF2Dept. of Neurosciences, CCF3Dept. of Neurology, CCF4Dept. of Pharmacol., Univ. ofKentucky, Lexington5Dept. of Cardiovasc. Med., CCFDianne M. Perez, Ph.D.Kunieda, T., Zuscik, M.J., Boongird, A., Perez, D.M., Lüders, H.O., and I.M. Najm (2002)Systemic overexpression of the α 1B-adrenergic receptor in mice: an animal model of epilepsy.Epilepsia 43:1324-1329.Papay, R., Zuscik, M.J., Ross, S.A., Yun, J., McCune, D.F., Gonzalez-Cabrera, P., Gaivin,R., Drazba, J., and D.M. Perez (2002) Mice expressing the α 1B-adrenergic receptor induces asynucleinopathy with excessive tyrosine nitration but decreased phosphorylation. J.Neurochem. 83:623-34.Yun, J., Zuscik, M.J., Gonzalez-Cabrera, P., McCune, D.F., Ross, S.A., Gaivin, R., Piascik,M.T., and D.M. Perez (2003) Gene expression profiling of α 1B-adrenergic receptor-inducedcardiac hypertrophy by oligonucleotide arrays. Cardiovasc. Res. 57:443-455.Gonzalez-Cabrera, P.J., Gaivin, R.J., Yun, J., Ross, S.A., Papay, R.S., McCune, D.F.,Rorabaugh, B.R., and D.M. Perez (2003) Genetic profiling of α 1-adrenergic receptor subtypesby oligonucleotide microarrays: coupling to interleukin-6 secretion but differences in STAT 3phosphorylation and gp-130. Mol. Pharmacol. 63:1104-1116.Yun, J., Gaivin, R.J., McCune, D.F., Atthaporn, B., Papay, R.S., Ying, Z., Gonzalez-Cabrera,P.J., Najm, I., and D.M. Perez (2003) Gene expression profiles of neurodegeneration inducedby the α 1B-adrenergic receptor: NMDA/ GABAA dysregulation and apoptosis. Brain Aug 22[epub aheadof print].127