Cell Line

The short form of D2 (D2S) and the long form (D2L) are two isoforms that contribute differentially to dopamine signaling in both prefrontal cortex and striatum. The D2 dopamine receptor, short form (D2s) has been shown to stimulate phospholipase D (PLD) activity independent of the activation of phospholipase C (PLC) activity in GH4 derived cells stably transfected with the D2s receptor. Agonist activation of D2s has been shown to mediate the inhibition of growth in the same cell line.

The neuropeptide galanin elicits a range of biological effects by interacting with specific G-protein-coupled receptors. Galanin receptors are seven-transmembrane proteins that have been shown to activate a variety of intracellular second-messenger pathways. GALR1 inhibits adenylyl cyclase via a G protein of the Gi/Go family. GALR1 is widely expressed in the brain, spinal cord, and peripheral sites including small intestine and heart.

Coupled exclusively Gq, MCH2 is a receptor for melanin-concentrating hormone. Other than regulating skin color, two subtypes (MCHR1 and MCHR2) are involved in energy homeostasis and social behaviors. In contrast to MCHR1 that is conserved among all mammals, functional MCHR2 is only expressed in carnivores and primates, but not in rodents.

The adrenoceptors ADRA2A is expressed in the brain, spleen, kidney, aorta, lung, skeletal muscle, heart and liver. ADRA2A -adrenoceptor knockout mice exhibit disruption of presynaptic inhibition of noradrenaline release at high stimulation frequencies. ADRA2A receptor is the principal autoreceptor in the presynaptic feedback loop regulating noradrenaline release. However, another α2 autoreceptor is also present.

Somatostatin receptors (SSTRs), a family of seven transmembrane (TM) domain G-protein-coupled receptors having five distinct subtypes (termed SSTR1-5), are activated by somatostatin secreted from the nerve and endocrine cells. SSTRs are widely expressed in many tissues, frequently as multiple subtypes that coexist in the same cell. With expressions in a tissue-specific manner, SSTRs are involved in the regulation of secretion of insulin, glucagon, and growth hormone as well as cell growth induced by neuronal excitation in both the central and peripheral nervous systems. The five receptors share common signaling pathways such as the inhibition of adenylyl cyclase, activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G-protein-dependent mechanisms. Aberrant expression of somatostatin receptors is known to be involved in a large number of human tumors. The human medullary thyroid carcinoma cell line TT expresses all SSTR s

Somatostatin receptors (SSTRs), a family of seven transmembrane (TM) domain G-protein-coupled receptors having five distinct subtypes (termed SSTR1–5), are activated by somatostatin secreted from the nerve and endocrine cells. SSTRs are widely expressed in many tissues, frequently as multiple subtypes that coexist in the same cell. With expressions in a tissue-specific manner, SSTRs are involved in the regulation of secretion of insulin, glucagon and growth hormone as well as cell growth induced by neuronal excitation in both the central and peripheral nervous systems. The five receptors share common signaling pathways such as the inhibition of adenylyl cyclase, activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G-protein-dependent mechanisms. Aberrant expression of somatostatin receptors is known to be involved in a large number of human tumors. The human medullary thyroid carcinoma cell line TT expresses all SSTR

Histamine receptor family consists of four members, namely, H1, H2, H3, and H4. The histamine H4 receptor is the most recently identified G protein-coupled histamine receptor that binds to several neuroactive drugs, including amitriptyline and clozapine. So far, H4 receptors have been found only on haematopoietic cells. This signifies its important role as a drug target for the treatment of inflammatory diseases.

Opioid receptors and their endogenous peptide ligands play important roles in the reward and reinforcement of drugs such as heroin, cocaine, and alcohol. The κ-opioid receptor is a type of opioid receptor which binds the peptide opioid dynorphin as the primary endogenous ligand. κ-opioid receptors are widely distributed in the brain, spinal cord, and in pain neurons. They are associated with the risk for alcohol dependence.

The cannabinoid receptor CNR1 is Gs-coupled GPCRs expressed in primarily CNS and some peripheral neurones; particularly prevalent in basal ganglia, hippocampus, cerebellum, cerebral cortex and also presented in some non-neuronal cells and tissues, for example leukocytes and testis. A shorter human splice variant (411aa) has been identified in the brain and other tissues by reverse-transcriptase PCR but mRNA levels were less than 10-fold the levels of the longer isoform. The pharmacological characteristics of the isoforms are similar.