Topic 02-Signaling-S_2011

Topic 02-Signaling-S_2011 - Endocrine signaling and...

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A. Click to edit Master subtitle style 2. Endocrine signaling and regulation Steroid hormone signaling B. Peptide hormone signaling C. Termination of signals D. Principles of Regulation
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Four paths to an endocrine Respons e H Endocrine response (distant) Autocrine (same cell) Paracrine  (nearby) In practice, it is difficult to tell the difference between paracrine & autocrine H H H H 22
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Hormone signaling § Initiated when hormone binds to receptor on target tissue § Type of receptor depends on hormone class § Peptide hormones Do not pass through membranes Receptors are on the cell surface § Steroids 33
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44 § Any cell can be exposed to any hormone § Specific responses are determined by proteins in the target cells § Receptors Endocrine responses are because it has  the  receptor Hormone H H Respons e H
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Specificity depends on the § Hormones can have >1 receptor Often a neural & an endocrine form They can cross react (1 receptor, 2 hormones) True of both steroids & peptides § Real life Most have >1 receptor & extensive 55
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Steroid signaling § Lipophilic Pass through membranes Receptors in the cytoplasm § Major mechanism Regulation of transcription Slow § Other mechanisms Direct regulation of cytoplasmic proteins Cell surface receptors Faster 66
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Conformation al change & nuclear localization Hormone Response Element dime r PolII Classic view: Direct activation § Hormone binding to receptor causes Conformational change Import to nucleus & dimerization Binds to HRE sequence mRN A 77
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Regulation of transcription through chromatin modification § Chromatin modification regulates transcription § Can result in activation & inhibition § Large regions influenced— Activatio n Inhibition 88
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Other mechanisms of steroid action 1. Cytoplasmic modulation 2. Cell surface receptor § & Steroid binding to either can lead to a signal involving modification of a protein(s) Signal or response n The importance is unclear n Know it exists 1 2 99
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The result of steroid action § ALL steroid hormones alter transcription Receptors all related Increases the synthesis of proteins through increasing transcription Can decrease the amount of a protein through transcriptional inhibition Indirect Protein turns over & is not replaced 1010
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Characteristics of protein hormone § Peptides do not enter cells in an active form § THEREFORE: Receptors must be on cell surface to bind hormone Results in a signal Signal leads to response § Classified by signaling mechanisms § Signals can modify any cellular process § Two major types G protein coupled 1111
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Protein hormones bind cell surface P H n Peptide = glycoprotein n Transmembrane proteins n Transduce response from outside the cell to inside the cell n Second messenger hypothesis 1212 H H H H 2nd messenger signal Respons
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§ Most common § All have 3 subunits: α, β, & γ (heterotrimeric) § Activation
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This note was uploaded on 02/22/2011 for the course PGY 452 taught by Professor Dr.baizer during the Spring '11 term at SUNY Buffalo.

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Topic 02-Signaling-S_2011 - Endocrine signaling and...

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