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Taste - The Organs of Taste - taste buds and Mechanisms of Taste Transduction

3 important questions on Taste - The Organs of Taste - taste buds and Mechanisms of Taste Transduction

What is the 4 step passage for salt and sour taste?

Na+ ions from salts and H+ from acidic “sour” substances enter the cell through amiloride-sensitive Na+ channels in the cell membrane and H+-sensitive TRP channels respectively. H+-sensitive TRP channels can either bind to or block other ion channels as well. This leads to depol of the taste bud.
Voltage gated Ca2+ channels open, allowing an influx of calcium into the cell
This influx triggers the release of neurotransmitters (such as serotonin) from synaptic vesicles
The neurotransmitter binds to receptors on gustatory afferent axons, inducing an action potential that carries the signal to the central nervous system

Sweet, bitter and umami tastes trigger a second messenger cascade but it still results in the release of neurotransmitters from synaptic vesicles which bind to receptors on gustatory afferent axons, inducing an action potential that carries the signal to the central nervous system.
What receptors do sweet, bitter and umami taste bind to?

Sweet: Tastants bind to a combination of T1R2 and T1R3 receptors
Umami: Amino acids bind to T1R1 and T1R3 receptors
Bitter: Substances bind to the T2R family of receptors, which are coupled to a G-protein called Gustducin

After sweet, bitter and umami taste bind to their specific receptors, name the 3 events that occur in the resultant cascade?

Binding activates phospholipase C (PLCB2) which generates IP3.
IP3 triggers the release of calcium (Ca2+ ) from internal stores (endoplasmic reticulum), which then opens TRPM5 channels.
This allows Na+ to enter the cell, leading to depolarization

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(RBM3640) Advanced Neurosciences

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