D103 LH lect20_C

D103 LH lect20_C - Lecture 20 Signaling V Todays Topics...

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Page 1 Lecture 20 –  Signaling  V Today’s Topics Receptor tyrosine Kinases Hormone nuclear receptors Integration of Signals Reading: MBOC5e, p889-891; 921-945
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Page 2 Signaling by steroid, thyroid, retinoid, vitamin D receptors Hormones are chemical messengers that coordinate cellular activity. Two major families  - steroid hormones, thyroid hormones / retinoids. Activate at  very low concentrations  - typically less than 1 ppb (1 ppb ~= 3 nM). The  small, hydrophobic  nature permits them to  diffuse through  the cell membrane. Steroid hormones can  persist  in  blood  for  hours,  in  fat  for  days . Over a hundred hormones function in a wide range of biological processes - e.g. reproduction  - e.g. estrogen, testosterone. metabolic rate  - thyroid hormone,  growth hormone. stress  - glucocorticoids, ACTH, CRF. blood pressure  - aldosterone, renin, angiotensin, vasopressin. calcium homeostasis  - vitamin D3, calcitonin, PTH. Some vitamins or vitamin derivatives are hormones, e.g. Vitamin A, Vitamin D3. Receptors are  ligand-modulated transcription factors – receptors that function in the  nucleus .
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Page 3 Nuclear hormone receptors super-family - general structure
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Page 4 Steroid hormone receptors - binding of ligand stimulates movement of  receptor-ligand complex into nucleus to bind to DNA  O H OH estradiol + ligand
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Page 5 Retinoid / thyroid / vitamin D hormone receptors - binding of ligand to  receptor in nucleus converts receptor from repressor to activator (represses transcription) (activates transcription) Note - unlike androgen and estrogen receptors, the  nuclear  localization signal  of the  retinoid / thyroid / vitamin D  hormone   receptors  is  always unmasked
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D103 LH lect20_C - Lecture 20 Signaling V Todays Topics...

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