Name two important functions of hormone receptors.
The number of receptors that respond to a hormone can change, resulting in increased or decreased cell sensitivity. The number of receptors can increase in response to rising hormone levels, called up-regulation, making the cell more sensitive to the hormone and allowing for more cellular activity. The number of receptors can also decrease in response to rising hormone levels, called down-regulation, leading to reduced cellular activity.
How can hormones mediate changes?
Depending on the location of the protein receptor on the target cell and the chemical structure of the hormone, hormones can mediate changes directly by binding to intracellular receptors and modulating gene transcription, or indirectly by binding to cell surface receptors and stimulating signaling pathways.
Why is cAMP-mediated signal amplification not required in steroid hormone signaling? Describe how steroid signaling is amplified instead.
In steroid hormone signaling, the steroid interacts directly with its intracellular receptor rather than signaling through a second messenger like cAMP. The steroid-receptor complex then moves into the nucleus, and directly regulates the transcription of DNA. This will cause the cell to produce multiple copies of the target gene, amplifying the signal from the hormone at the transcriptional level rather than the second messenger level.