Receptors Flashcards
test 3 material
what is a general feature of all receptors?
they have a ligand that binds at the active site
cell-impermeant: binds extracellularly (NT)
cell-permeant: cross cell membrane and binds (cortisol, hormones)
undergo transduction via an effector molecule
what is transduction and what are the different types?
transduction is the transformation from one type of energy to another
chemical -> electrical (ionotropic receptors)
chemical -> intracellular signal transduction (enzyme-linked, intracellular, and GPCRs)
what are the four types of receptors?
ionotropic, enzyme-linked, intracellular, and G-protein coupled receptors
how do ionotropic receptors work?
ions flow into and out of the cell to either cause EPSPs (if depolarized) or IPSPs (if hyperpolarized), rapid onset/offset
how do enzyme-linked receptors work?
metabotropic signal-gated receptors that bind brain derived neuro factor (BDNF) or other growth hormones at their extracellular active site, the signal links the two halves of the receptor and the enzyme is activated, enzyme causes cascade that triggers transcription factors to alter gene expression, slow, enduring effect
how do intracellular receptors work?
receptors in cytoplasm are activated by cell-permeable hormones, DNA binding domain is then exposed and the complex translocates to nucleus and alters gene transcription
what are the two types of G-protein coupled receptors?
monomeric GPCRs and heterotrimeric GPCRs
how do monomeric GPCRs work?
ligand binds to the receptor outside cell which activates GEF that is bound to the receptor on the inside of the cell, GEF removes GDP from G-protein inside cell which allows GTP to bind to the G-protein, GTP activates the G protein and a signaling cascade takes place, GAP removes a phosphate from GTP to convert it to GDP which inactivates the G-protein it is attached to
how do heterotrimeric GPCRs work?
ligand binds to the receptor and GDP-bound G-protein associates with the receptor, GDP is replaced with GTP, G-alpha + GTP dissociate from G-beta and start signaling cascades, GTP is hydrolyzed into GDP by GAP and G-alpha + GDP associate with G-beta again and they all become inactive
what are the two pathways of heterotrimeric GPCRs?
shortcut pathways and second-messenger pathway
what is the shortcut pathway of heterotrimeric GPCRs?
G-beta activate G-gated ion channel, G-alpha activates G-gated Na+ and Ca2+ channels, no second messenger needed, faster and more localized
what is the second-messenger pathway of heterotrimeric GPCRs?
3 types of G-alpha bind to enzymes which release second messengers in order to activate 3 main signaling pathways, slower and less localized
what are the three types of second-messenger pathways?
Gs, Gq, and Gi/o
how does the Gs second-messenger pathway work?
norepinephrine binds to B-adrenergic receptor which forms the effector molecule adenylyl cyclase, this activates the second messenger cAMP which activates the late effect protein kinase A which increases protein phosphorylation
how does the Gq second-messenger pathway work?
glutamate binds to mGluR which makes phospholipase C, which makes either diacylglycerol and then protein kinase C or IP3 and then releases Ca2+, both ways increase protein phosphorylation and activate calcium-binding proteins
