Transporters Flashcards
Mechanisms of movement across a membrane
Diffusion
Facilitated diffusion
Active transport
Endocytosis
Exocytosis
Diffusion
the passive movement of molecules from areas of high concentration to areas of low concentration, down their concentration gradient.
Facilitated diffusion
the passive movement of molecules across the membrane with the help of a transport protein.
Active transport
the movement of molecules against their concentration gradient, requiring energy in the form of ATP.
Endocytosis
the process by which molecules or particles are taken up by the cell, through the formation of a vesicle.
Exocytosis
the process by which molecules or particles are released from the cell, through the fusion of a vesicle with the membrane.
Neurotransmitter transporters in the nervous system
Neurotransmitter transporters are membrane proteins that regulate the concentration of neurotransmitters in the synaptic cleft.
Major neurotransmitter transporters in the nervous system include the serotonin transporter (SERT), dopamine transporter (DAT), norepinephrine transporter (NET), and GABA transporter (GAT).
These transporters are located on the presynaptic terminal of neurons and are responsible for the reuptake of released neurotransmitters.
They have 12 transmembrane domains and can exist in different conformations, allowing them to transport neurotransmitters across the membrane.
Role of presynaptic neurotransmitter reuptake
Presynaptic neurotransmitter reuptake is the process by which neurotransmitters are transported back into the presynaptic terminal.
This process is mediated by neurotransmitter transporters, such as SERT, DAT, and NET.
It is important for the termination of neurotransmitter signaling and the regulation of synaptic transmission.
Defects in presynaptic reuptake can lead to various neurological and psychiatric disorders.
Glial cell neurotransmitter reuptake and the glutamate shuttle
Glial cells also play a role in neurotransmitter reuptake, particularly for glutamate, the main excitatory neurotransmitter in the brain.
Glial cells express the glutamate transporter GLT-1, which is responsible for the reuptake of glutamate from the synaptic cleft.
The glutamate shuttle is a mechanism by which glutamate is transported from neurons to glial cells, where it is converted to glutamine by the enzyme glutamine synthetase.
Glutamine is then transported back to neurons, where it is converted back to glutamate and used for neurotransmission.
Importance of neurotransmitter transporters in non-vesicular neurotransmitter release
Non-vesicular neurotransmitter release refers to the release of neurotransmitters from sources other than synaptic vesicles.
This includes the release of neurotransmitters from glial cells and neurons, as well as from non-neuronal cells.
Neurotransmitter transporters play an important role in regulating non-vesicular neurotransmitter release by controlling the concentration of neurotransmitters in the extracellular space.
Dysregulation of non-vesicular neurotransmitter release has been implicated in various neurological and psychiatric disorders.
Drugs that act on transporters
Tiagabine is a drug that inhibits the GABA transporter, increasing the concentration of GABA in the synaptic cleft and enhancing inhibitory neurotransmission.
Fluoxetine is a selective serotonin reuptake inhibitor (SSRI), which blocks the reuptake of serotonin by SERT, leading to increased serotonin levels in the synaptic cleft and enhanced serotonin signaling.
Cocaine and amphetamine are drugs that act on amine transporters, such as DAT and NET, increasing the levels of dopamine and norepineph
