G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors and critical regulators of mammalian physiology. They detect a wide range of stimuli, including odorants, neurotransmitters, hormones, and lipids, and are the most targeted class of drugs, accounting for over 30% of all prescription drugs. The traditional view that GPCR signaling occurs exclusively at the cell surface has been revised, with evidence showing that GPCRs can also signal from intracellular compartments, leading to distinct cellular and physiological outcomes. The classical model of GPCR signaling at the cell surface has been replaced by a spatially encoded model, where GPCR signaling is compartmentalized, and the subcellular location of activation determines the signaling outcome. This model highlights the complexity of GPCR signaling, with intracellular compartments such as endosomes, Golgi, and mitochondria playing key roles. For example, endosomal signaling can lead to unique transcriptional and phospho-signaling responses, and the location of signaling, rather than the total amount of second messengers, dictates the outcome. Intracellular GPCR signaling is influenced by various factors, including the presence of different G proteins, the kinetics of signaling, and the trafficking routes of receptors. The endosome is a key compartment for GPCR signaling, with unique biophysical properties such as pH and lipid composition that influence receptor activity. The acidic pH of endosomes and the presence of specific phospholipids can affect GPCR signaling, while the spatial arrangement of endosomes can influence the propagation of signals. The spatial encoding of GPCR signaling has important physiological and therapeutic implications. It allows for the differentiation of signals based on the location of activation, which can be exploited to develop more targeted therapies. For example, the use of ligands with different pharmacodynamic properties can selectively target receptors at specific compartments, leading to distinct physiological outcomes. Additionally, the regulation of GPCR signaling by intracellular compartments such as the endosome and Golgi can be manipulated to treat diseases, such as cardiac hypertrophy and neuropathic pain. The study of intracellular GPCR signaling is an active area of research, with ongoing efforts to understand the mechanisms and regulation of compartmentalized signaling. The findings highlight the importance of spatial encoding in GPCR signaling and its potential for therapeutic applications. Further research is needed to fully understand the role of intracellular GPCR signaling in physiological and pathological processes, and to develop more effective treatments for diseases.G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors and critical regulators of mammalian physiology. They detect a wide range of stimuli, including odorants, neurotransmitters, hormones, and lipids, and are the most targeted class of drugs, accounting for over 30% of all prescription drugs. The traditional view that GPCR signaling occurs exclusively at the cell surface has been revised, with evidence showing that GPCRs can also signal from intracellular compartments, leading to distinct cellular and physiological outcomes. The classical model of GPCR signaling at the cell surface has been replaced by a spatially encoded model, where GPCR signaling is compartmentalized, and the subcellular location of activation determines the signaling outcome. This model highlights the complexity of GPCR signaling, with intracellular compartments such as endosomes, Golgi, and mitochondria playing key roles. For example, endosomal signaling can lead to unique transcriptional and phospho-signaling responses, and the location of signaling, rather than the total amount of second messengers, dictates the outcome. Intracellular GPCR signaling is influenced by various factors, including the presence of different G proteins, the kinetics of signaling, and the trafficking routes of receptors. The endosome is a key compartment for GPCR signaling, with unique biophysical properties such as pH and lipid composition that influence receptor activity. The acidic pH of endosomes and the presence of specific phospholipids can affect GPCR signaling, while the spatial arrangement of endosomes can influence the propagation of signals. The spatial encoding of GPCR signaling has important physiological and therapeutic implications. It allows for the differentiation of signals based on the location of activation, which can be exploited to develop more targeted therapies. For example, the use of ligands with different pharmacodynamic properties can selectively target receptors at specific compartments, leading to distinct physiological outcomes. Additionally, the regulation of GPCR signaling by intracellular compartments such as the endosome and Golgi can be manipulated to treat diseases, such as cardiac hypertrophy and neuropathic pain. The study of intracellular GPCR signaling is an active area of research, with ongoing efforts to understand the mechanisms and regulation of compartmentalized signaling. The findings highlight the importance of spatial encoding in GPCR signaling and its potential for therapeutic applications. Further research is needed to fully understand the role of intracellular GPCR signaling in physiological and pathological processes, and to develop more effective treatments for diseases.