Receptors are specialized protein molecules located on the surface of or within cells, serving as crucial components for cellular communication and signal transduction. They bind to specific molecules such as hormones, neurotransmitters, or other signaling molecules, triggering a cascade of biological responses essential for maintaining physiological processes.
There are various types of receptors, each with distinct functions. Cell surface receptors, such as G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs), are embedded in the plasma membrane. GPCRs, the largest family of receptors, mediate a wide range of cellular responses by activating intracellular G-proteins. RTKs, on the other hand, are involved in regulating cell growth, differentiation, and metabolism by phosphorylating tyrosine residues on themselves and other proteins upon ligand binding.
Intracellular receptors, such as steroid hormone receptors, reside within the cell and interact with lipophilic molecules that can cross the cell membrane. Upon binding to their ligands, these receptors typically function as transcription factors, directly influencing gene expression and thereby modulating cellular activity.
Receptors play a fundamental role in the body's ability to respond to external and internal stimuli. Dysregulation of receptor function can lead to various diseases, including cancer, diabetes, and autoimmune disorders. Consequently, many therapeutic drugs are designed to target specific receptors, aiming to correct or modify their activity to treat diseases effectively.