GPCR & G Protein 信号通路图概览
GPCR constitutes a large protein family of receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses. G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins involved in transmitting signals from a variety of different stimuli outside a cell into the inside of the cell. GPCRs are activated by diverse stimuli, including light, enzymatic processing of their N-termini, and binding of proteins, peptides, or small molecules such as neurotransmitters, and regulate neuronal excitability by indirectly modulating the function of voltage-gated channels, such as voltage-gated calcium channel and transient receptor potential (TRP) ion channels. In unstimulated cells, the state of G alpha is defined by its interaction with GDP, G beta-gamma, and a GPCR. Upon receptor stimulation by a ligand, G alpha dissociates from the receptor and G beta-gamma, and GTP is exchanged for the bound GDP, which leads to G alpha activation.