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The Endocrine System: Hormones and Gene Expression

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.

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The Endocrine System: Hormones and Gene Expression

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  1. The Endocrine System: Hormones and Gene Expression Samuel Yang Henok Daniel 4/3/13

  2. 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.

  3. Steroid hormones directly regulate gene expression.

  4. 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: • A specific receptor protein on the plasma membrane is activated by a hormone • A second messenger relays the signal into the cell, which produced a physiological response. • For cell-surface proteins -------->

  5. 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

  6. 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

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  8. 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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