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The Endocrine System: Hormones and Gene Expression. Samuel Yang Henok Daniel 4/3/13. Background : Hormone Receptors and Gene Expression. In the 1970s, experiments suggested that estradiol and various other steroid affect gene transcription after they bind to their receptors. - PowerPoint PPT Presentation
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The Endocrine System: Hormones and Gene Expression
Samuel YangHenok Daniel
4/3/13
Background: Hormone Receptors and Gene Expression
• In the 1970s, experiments suggested that estradiol and various other steroid affect gene transcription after they bind to their receptors.
• It was discovered that inside a steroid hormone receptor, there was a distinctive DNA-binding region known as a zinc finger.– It was also confirmed that steroid-hormone receptors bind to specific spots on
DNA called hormone-response elements.
• After binding to the hormone-response element, the hormone receptor complex binds to DNA, which induces transcription.
• mRNA transcripts are produced, amplifying hormone signal.• Each transcript is translated many times.
• Steroid hormones directly regulate gene expression.
Signal Transduction• Signal Transduction is the phenomenon that allows a message
from a hormone to be changed into a form that is active inside the cell.
• Signal Transduction is broken down into two stages:1. A specific receptor protein on the plasma membrane is activated by a hormone2. A second messenger relays the signal into the cell, which produced a physiological
response.
1. For cell-surface proteins -------->
cAMP: Second Messenger
• cAMP – Cyclic adenosine monophosphate– It is considered a second messenger (non-protein
signal) that increases in concentration inside the cell
– So as a hormone binds to receptor in the cell, the activation of a G protein occurs.
– Synthesis of cAMP from ATP occurs by adenylyl cyclase enzyme• cAMP transfers the signal from the cell surface to the
signaling cascade in the cell
Signaling Cascade: Amplification
• The signaling cascade consists of a series of steps that serve the purpose to amplify a signal from a hormone.
• cAMP bind to protein kinase A• The protein kinase A then activates molecules
of phosphorylase kinase• Phosphorylase kinase activates molecules of
phosphorylase
Presentation
Signaling Cascade: Amplification
• Alpha-1 receptors– Calcium ions and IP3 (inositol triphosphate) serve
as both messenger molecules
– Diacylglycerol (DAG) and cyclic GMP (cGMP) are also second messengers
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