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α1-Adrenoceptor Subtype Selectivity and Lower Urinary Tract Symptoms
Debra A. Schwinn, MD, David T. Price, MD, Perinchery Narayan, MD Mayo Clinic Proceedings Volume 79, Issue 11, Pages (November 2004) DOI: / Copyright © 2004 Mayo Foundation for Medical Education and Research Terms and Conditions
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FIGURE 1 Schematic model of the α1a -adrenoceptor depicts the 7 transmembrane domains (TM1-TM7) with an extracellular amino (NH2) and an intracellular carboxyl (COOH) terminus. Adapted from Trends Pharmacol Sci,5 with permission from Elsevier. Mayo Clinic Proceedings , DOI: ( / ) Copyright © 2004 Mayo Foundation for Medical Education and Research Terms and Conditions
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FIGURE 2 Ligand-binding sites and signaling. Key residues important for α1-adrenoceptor agonist binding (red circles) and antagonist binding (green circles). A salt bridge is formed between amino acid D106 (red and black striped circle, also identified as an important residue in agonist binding) in transmembrane domain (TM) 3 and K309 (black circle) in TM7, stabilizing the 3-dimensional structure. This model was based on results of several mutagenetic studies. Signaling pathways also are schematized. α1-Adrenoceptors couple to the G protein, Gq, and then activate phospholipase C-β (PLC-β), which hydrolizes membrane phospholipids. The main 2 products are inositol trisphosphate (IP3) and diacylglycerol (DAG); IP3 activates IP3 receptors on the sarcoplasmic reticulum to release calcium from intracellular stores, whereas DAG activates protein kinase C (PKC), which phosphorylates proteins (circled “P”) for more long-term cellular responses. ER = endoplasmic reticulum; NH2 = extracellular amino terminus; COOH = intracellular carboxyl terminus. Mayo Clinic Proceedings , DOI: ( / ) Copyright © 2004 Mayo Foundation for Medical Education and Research Terms and Conditions
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FIGURE 3 Genomic organization of the human α1a-adrenoceptor isoforms. Top, Schematic representation of the human a1aAR gene; boxes represent exons and lines represent introns. The numbers below the boxes and lines represent approximate lengths of exons and introns in nucleotide base pairs. Bottom, Location of splice sites and amino acid sequences at the amino terminus, donor and acceptor sites, and carboxyl termini. The full-size lengths of each splice variant product are shown in parentheses. aa = amino acids; kb = kilobases. Adapted from FEBS Lett,24 with permission. Mayo Clinic Proceedings , DOI: ( / ) Copyright © 2004 Mayo Foundation for Medical Education and Research Terms and Conditions
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FIGURE 4 Distribution of α1a-adrenoceptor messenger RNA in human prostate. Left, Photomicrograph of human prostate tissue reveals glandular (open arrows) and stromal (solid arrows) compartments of the prostate (hematoxylin-eosin, original magnification ×100). Right, In situ hybridization of the same slide, visualized with darkfield microscopy, shows α1a-adrenoceptor messenger RNA predominantly in the stromal compartment of this tissue (solid arrows). From J Urol,30 with permission. Mayo Clinic Proceedings , DOI: ( / ) Copyright © 2004 Mayo Foundation for Medical Education and Research Terms and Conditions
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