Heterotrimeric G proteins are key intracellular coordinators that receive signals from cells through activation of cognate G protein-coupled receptors (GPCRs). The details of their atomic interactions and structural mechanisms have been described by many biochemical and biophysical studies. Specifically, a framework for understanding conformational changes in the receptor upon ligand binding and associated G protein activation was provided by description of the crystal structure of the β2-adrenoceptor-Gs complex in 2011. This review focused on recent findings in the conformational dynamics of G proteins and GPCRs during activation processes.
GTP-Binding Proteins* ; Heterotrimeric GTP-Binding Proteins

No abstract available.
GTP-Binding Proteins*

No abstract available.
GTP-Binding Proteins

No Abstract Available.
GTP-Binding Proteins* ; Receptors, Cell Surface*

G protein-coupled receptors (GPCRs) are membrane receptors; approximately 40% of drugs on the market target GPCRs. A precise understanding of the activation mechanism of GPCRs would facilitate the development of more effective and less toxic drugs. Heterotrimeric G proteins are important molecular switches in GPCR-mediated signal transduction. An agonist-activated receptor interacts with specific sites on G proteins and promotes the release of GDP from the Galpha subunit. Because of the important biological role of the GPCR-G protein coupling, conformational changes in the G protein upon receptor coupling have been of great interest. One of the most important questions was the interface between the GPCR and G proteins and the structural mechanism of GPCR-induced G protein activation. A number of biochemical and biophysical studies have been performed since the late 80s to address these questions; there was a significant breakthrough in 2011 when the crystal structure of a GPCR-G protein complex was solved. This review discusses the structural aspects of GPCR-G protein coupling by comparing the results of previous biochemical and biophysical studies to the GPCR-G protein crystal structure.
GTP-Binding Proteins ; Guanosine Diphosphate ; Heterotrimeric GTP-Binding Proteins ; Membranes ; Signal Transduction

The regulators of the G protein signaling (RGS) proteins are responsible for the rapid acceleration of the GTPase-activity intrinsic to the heterotrimeric G protein alpha subunits. As GTPase-activating proteins (GAP), the RGS proteins negatively regulate the G-protein signals. Recently, the RGS proteins are known to be one of the important regulators of opioid signal transduction and the development of tolerance. The aim of this study was to review the recent discovery and understanding of the role of RGS proteins in opioid signaling and the development of tolerance. This information will be useful for medical personnel, particularly those involved in anesthesia and pain medicine, by helping them improve the effective use of opioids and develop new drugs that can prevent opioid tolerance.
Acceleration ; Analgesics, Opioid ; Anesthesia ; GTP-Binding Protein alpha Subunits ; GTP-Binding Proteins ; GTPase-Activating Proteins ; RGS Proteins* ; Signal Transduction

GTP-Binding Proteins ; Receptors, Thyrotropin-Releasing Hormone ; Thyrotropin-Releasing Hormone*

ACTH-independent macronodular adrenal hyperplasia (AIMAH) is an uncommon cause of Cushing's syndrome (CS). The pathophysiology of this disorder is heterogeneous in its molecular origin and also in its clinical presentation. AIMAH can present mainly as an incidental radiological finding with sub-clinical CS or rarely with overt CS. In a few familial cases reported with AIMAH, specific aberrant G-protein coupled receptors were expressed in the adrenals of all affected members, but sporadic cases are more common. The aberrant adrenal function of G-protein coupled receptors can lead to cell proliferation and abnormal regulation of steroidogenesis. Unilateral or bilateral adrenalectomy has been the most frequently used treatment for this adrenal disorder; alternatively, the identification of aberrant receptors using in vivo protocol of investigation can offer specific pharmacological approach to control abnormal steroidogenesis and possibly prevent AIMAH progression.
Adrenalectomy ; Cell Proliferation ; Cushing Syndrome ; GTP-Binding Proteins ; Hyperplasia

No Abstract Available.
Adenylyl Cyclases* ; GTP-Binding Proteins* ; Receptors, Cell Surface*

Heterotrimeric G proteins mediate signals generated by neurotransmitters and hormones. Among G proteins, Go is found in a large quantity in brain and growth cone membranes of neurons. In spite of its abundance in neurons, the role of Go is not fully understood. In the previous study, we showed that transient expression of the alpha subunit of Go (alpha o) modulated neurite outgrowth in F11 cells. It is possible that transient transfection may cause transient accumulation of the protein, which itself may alter differentiation process in non-specific manner. In this study, we determined that modulation of neurite outgrowth by alpha o was specific by evaluating the effect of alpha o in stably transformed F11 cells. F11 cells stably expressing the wild type alpha o (alphao(wt)) and a constitutively active form of alpha o (alpha oQ205L) were established. In normal F11 cells and alpha o-stable cell lines, the neurite length was measured in the presence of dibutyryl cAMP. In normal F11 cells, the average length of neurites was 57.9+/-7.0 microgram. In alpha o(wt)- and alpha o(Q205L)-expressing cells, the average length were 34.4+/-5.1 microgram 30.5+/-3.6 microgram, respectively. Thus, stable expression of alpha o(wt) and alpha o(Q205L) caused a decrease in neurite outgrowth by 40.6%, 47.3% respectively. This result indicates that modulation of neurite by alpha o was specific to the function of alpha o but not due to accumulation of exogenous proteins.
Brain ; Cell Line ; Growth Cones ; GTP-Binding Proteins ; Heterotrimeric GTP-Binding Proteins ; Membranes ; Neurites* ; Neurons ; Neurotransmitter Agents ; Transfection