Hormone receptors types

Penalva RG, Flachskamm C, Zimmermann S, Wurst W, Holsboer F, Reul JMHM, Linthorst ACE (2002) Corticotropin-releasing hormone receptor type 1-deficiency enhances hippocampal serotonergic neurotransmission an in vivo microdialysis study in mutant mice. Nemoscience 109 253-266... 

Skutella T, Probst JC, Renner U, Holsboer F, Behl C (1998) Corticotropin-releasing hormone receptor (type 1) antisense targeting reduces anxiety. Neuroscience 85 795-805... 

Skutella T, Montkowski A, Stohr T, Probst JC, Landgraf R, Holsboer F, Jirikowski GF (1994) Corticotropin-releasing hormone oligodeoxynucleotide treatment attenuates social defeat-induced anxiety in rats. Cell Mol Neurobiol 14 579-588 Skutella T, Probst JC, Renner U, Holsboer F, Behl C (1998) Corticotropin-releasing hormone receptor (type I) antisense targeting reduces anxiety. Neuroscience 85 795-805... 

Oxytocin and Vasopressin Receptors. The actions of oxytocin and vasopressin are mediated through their interactions with receptors. Different receptor types as well as different second messenger responses help explain their diverse activities in spite of the hormones stmctural similarities. Thus oxytocin has at least one separate receptor and vasopressin has been shown to have two principal receptor types, and V2. Subclasses of these receptors have been demonstrated, and species differences further compHcate experimental analysis. It is apparent that both oxytocin and receptors function through the GP/1 phosphoHpase C complex (75), while the V2 receptors activate cycHc AMP (76). 

Thyroid hormone receptors (THRs) are subdivided intoa and P types, each having two isoforms. In rat brain, THR, mRNA is present in hippocampus, hypothalmus, cortex, cerebellum, and amygdala. Thyroxine (l-T (284) and triiodothyronine (l-T ) (285) are endogenous ligands for the THRs. TRIAC (286) is a THR antagonist. Selective ligands for PPARs have yet to be identified (Table 16). 

The process by which cells take up large molecules is called endocytosis. Some of these molecules (eg, polysaccharides, proteins, and polynucleotides), when hydrolyzed inside the cell, yield nutrients. Endocytosis provides a mechanism for regulating the content of certain membrane components, hormone receptors being a case in point. Endocytosis can be used to learn more about how cells function. DNA from one cell type can be used to transfect a different cell and alter the latter s function or phenotype. A specific gene is often employed in these experiments, and this provides a unique way to smdy and analyze the regulation of that gene. DNA transfection depends upon endocytosis endocy-... 

A comparison of several different steroid receptors with thyroid hormone receptors revealed a remarkable conservation of the amino acid sequence in certain regions, particularly in the DNA-binding domains. This led to the realization that receptors of the steroid or thyroid type are members of a large superfamily of nuclear receptors. Many related members of this family have no known ligand at present and thus are called orphan receptors. The nuclear receptor superfamily plays a critical role in the regulation of gene transcription by hormones, as described in Chapter 43. 

The family of heterotrimeric G proteins is involved in transmembrane signaling in the nervous system, with certain exceptions. The exceptions are instances of synaptic transmission mediated via receptors that contain intrinsic enzymatic activity, such as tyrosine kinase or guanylyl cyclase, or via receptors that form ion channels (see Ch. 10). Heterotrimeric G proteins were first identified, named and characterized by Alfred Gilman, Martin Rodbell and others close to 20 years ago. They consist of three distinct subunits, a, (3 and y. These proteins couple the activation of diverse types of plasmalemma receptor to a variety of intracellular processes. In fact, most types of neurotransmitter and peptide hormone receptor, as well as many cytokine and chemokine receptors, fall into a superfamily of structurally related molecules, termed G-protein-coupled receptors. These receptors are named for the role of G proteins in mediating the varied biological effects of the receptors (see Ch. 10). Consequently, numerous effector proteins are influenced by these heterotrimeric G proteins ion channels adenylyl cyclase phosphodiesterase (PDE) phosphoinositide-specific phospholipase C (PI-PLC), which catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) and phospholipase A2 (PLA2), which catalyzes the hydrolysis of membrane phospholipids to yield arachidonic acid. In addition, these G proteins have been implicated in... 

Hsia SC, Shi YB (2002) Chromatin disruption and histone acetylation in regulation of the human immunodeficiency virus type 1 long terminal repeat by thyroid hormone receptor. Mol Cell Biol 22 4043-4052... 

Figure 7.4 The effect of bile acids on energy expenditure. Circulating bile acids bind to the G-protein-coupled receptor, TGR5 that stimulates increased cAMP-PKA activation and increased expression of type-2 iodothyronine deiodinase (D2). This response is sensitised by a high-fat diet. D2 converts thyroxine (T4) to active 3,5,3 -tri-iodothyronine (T3). T3 stimulates thyroid hormone receptor binding to target genes. This leads to altered expression of genes associated with energy balance, and increased energy expenditure.

Ga-GDP has no affinity for the effector protein and reassociates with the p and Y subunits (A). G-proteins can undergo lateral diffusion in the membrane they are not assigned to individual receptor proteins. However, a relation exists between receptor types and G-protein types (B). Furthermore, the a-subunits of individual G-proteins are distinct in terms of their affinity for different effector proteins, as well as the kind of influence exerted on the effector protein. G -GTP of the Gs-protein stimulates adenylate cyclase, whereas G -GTP of the Gr protein is inhibitory. The G-protein-coupled receptor family includes muscarinic cholinoceptors, adrenoceptors for norepinephrine and epinephrine, receptors for dopamine, histamine, serotonin, glutamate, GABA, morphine, prostaglandins, leukotrienes, and many other mediators and hormones. 

Hormone antagonism Application of drugs that bind to and inhibit the steroid hormone receptors or different types of releasing hormone receptors... 

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