All ionotropic glutamate receptors contain 5 pore forming subunits
Group of answer choices True False
The correct answer and explanation is:
Correct Answer: False
Explanation:
Ionotropic glutamate receptors do not contain five pore-forming subunits. Instead, they are typically tetrameric, meaning they consist of four subunits.
What Are Ionotropic Glutamate Receptors?
Ionotropic glutamate receptors are ligand-gated ion channels that mediate fast synaptic transmission in the central nervous system. They are activated by the neurotransmitter glutamate, and once activated, they allow ions (such as Na⁺, K⁺, or Ca²⁺) to pass through the cell membrane, leading to excitation of the neuron.
There are three main types:
- AMPA receptors
- NMDA receptors
- Kainate receptors
Each of these receptor types is made up of four subunits that come together to form a central ion channel or pore. These subunits can be different combinations of receptor-specific subunits:
- AMPA: GluA1–GluA4
- NMDA: GluN1, GluN2A-D, GluN3A-B
- Kainate: GluK1–GluK5
Tetrameric Structure
Each ionotropic glutamate receptor has four transmembrane subunits arranged symmetrically around a central pore. This structure is essential for their function as ion channels. Crystallographic and electron microscopy studies have confirmed this tetrameric arrangement, which is critical for their ion selectivity and gating mechanisms.
Why the Confusion?
People often confuse ionotropic glutamate receptors with other ion channels like GABA_A receptors or nicotinic acetylcholine receptors, which are pentameric (contain five subunits). However, this structural difference is key in distinguishing receptor types and understanding their roles in neural signaling.
Conclusion:
It is incorrect to say that all ionotropic glutamate receptors contain five pore-forming subunits. The correct structure involves four subunits, making the statement false.