Cell Surface Receptors
Cell surface receptors regulate a multitude of biological pathways required for cell growth, differentiation, proliferation, and survival. Because of the critical nature of these pathways, it is not surprising that mutations in cell surface receptors are responsible for a wide array of diseases, including cancers, neurodegeneration, achondroplasia and atherosclerosis. In fact, nearly half of all drugs in clinical use target cell surface receptors, and these proteins and their ligands remain extremely important targets for structure-based drug design and novel drug development.
Cell Surface Receptors are divided into 3 major classes: ion channel-linked receptors, enzyme-linked receptors, and G protein-coupled receptors. Ion channels are pore-forming proteins present in the membranes of all cells. Ions pass through channels down their electrochemical gradient, without the requirement for ATP or metabolic energy. Ion channels are especially prominent components of the nervous system, since "transmitter-activated" channels mediate conduction across nerve synapses.
Ion channels are also key components in the cellular response to toxins and venoms, as well as biological processes that involve rapid changes in cells, such as cardiac, skeletal, and smooth muscle contraction, T-cell activation and hormone release.
Enzyme-linked receptors are usually single-pass transmembrane receptors. This group includes the highly studied receptor tyrosine kinases RTKs , which bind to polypeptide growth factors that control cell proliferation and differentiation. G-protein-coupled receptors GPCRs , also known as 7 transmembrane 7-TM receptors, are structurally and functionally related proteins characterized by seven membrane-spanning a helices.
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GPCRs are involved in numerous signaling pathways, including sensory perception sight, smell, taste, pain. Previous Figure Next Figure. Email or Customer ID. Forgot password? Old Password.
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Enter your email address below and we will send you your username. Based on meta-analysis of over studies of transmembrane cell-surface receptors, as well as his own research, Prof.
Maruyama proposed a new model for receptor activation -- the "rotation model. Cell contents are separated and protected from the external environment by cell membranes.
Cell surface receptor
Survival and reproduction of living organisms depend upon proper perception and processing of environmental signals. Cell-surface receptors are proteins embedded in the cell membrane. They are responsible for communication between the cell and everything around it.
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These receptors are highly specialised and respond only to specific molecules, ignoring all others. Therefore, there are many different kinds of receptors.
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For example, humans have over a thousand encoded in their genome. However, the basic mechanism of activation is the same for all receptors: a ligand -- for example a hormone, growth factor, cytokine, or nutrient -- binds to the receptor and triggers changes in the cell's metabolism and activity.
Ligand binding is a very basic biological process crucial to all functions of a living organism. Abnormal activation of receptors is often implicated in cancers, and developmental and mental diseases. Therefore, understanding of ligand binding is essential for pharmaceutical research and may result in better drugs -- lower doses, greater effectiveness, and fewer side-effects. Drugs are essentially molecules that can interact with receptors and participate in ligand binding, triggering desired cell responses. Drugs often mimic natural ligands and can be seen as part-time workers substituting for staff members who did not show up to work.
Who wants workers who do not do what they were hired to do?
According to the previous "dimerization" model, prior to ligand binding receptors exist in monomeric form.