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: 1.A specific receptor protein on the plasma membrane is activated by a hormone 2.A second messenger relays the signal into the cell, which produced a physiological response. 1.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

7. Presentation

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