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Phosphoinositide cascade generates which second messengers
Diacylglycerol (DAG) and Inositol triphosphate (IP3)
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DAG is an activator for?
Protein kinase C
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IP3 causes release of?
Ca2+, 3rd messenger from intracellular stores
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Steroid hormones produce effects how
directly binding and inducing transcription of genes
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Eicosanoids
- 20 carbon unsaturated fatty acids derived from arachidonic acid
- -Arachidonic acid derived from linoleic acid, essential fatty acid
- Hormone-like biomodulator substances
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Types of lipids
Storage, Membrane Lipids, Hormones, Fat Soluble Vitamins, Bile acids, Waxes, Pigments, Scents, ect.
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Types of Storage Lipids
Neutral Fat: Triacylglycerols
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Membrane Lipids
Polar Lipids: Phospholipids, Glycolipids, Sphingolipids, Sterols
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Types of Hormone Lipids
Steroids, Prostaglandins
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Types of Fat Soluble Lipids
A, D, K
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PIP2 is cleaved into what
DG and IP3
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Phosphoinositide cascade Step 1
- Hormone binds to receptor
- GDP bound to GP to become GTP
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Phosphoinositide cascade Step 2
GTP bounded G P moves to Phospholipase C (PLC) and activates it
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Phosphoinositide cascade Step 3
- Active PLC cleaves PIP2 into IP3 and DG
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Phosphoinositide cascade Step 4
IP 3 binds to a specific receptor on ER, releasing Ca 2+
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Phosphoinositide cascade Step 5
- DG and Ca2+ activate PKC on plasma membrane
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Phosphoinositide cascade Step 6
- PKC phosphorylates cellular proteins, producing the response to the hormones
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Effects mediated by Phosphoinositide cascade
- Glycogenlysis in liver
- Histamine secretion of mast cells
- Serotonin release by blood platelets
- Smooth muscle contraction
- Visual transduction in invertebrate photo-receptors
- Insulin secretion by pancraetic islet cells
- ect.
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Steroid hormone formation
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Cortisol
- -Affects protein and carbohydrate metabolism
- -Suppresses immune response, inflammation, and allergic responses.
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Aldosterone
- Regulates re-absorption of
- Na+, Cl-, HCO3- in the kidney
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Testosterone/Estradiol
- -Male and female sex hormones.
- -Influence secondary sexual characteristics.
- -Regulate female reproductive cycle.
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Steroid Hormone Receptors share?
Substantial sequence homology/functional domain substructure
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Model for Steroid Receptor Action
- Serum binding protein carries hormone to plasma membrane
- Steroid enters cell, enters nucleus
- Steroid binds receptor on DNA, prompts transcription of mRNA
- Translation into new protein
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Examples of specificity of steroid receptor binding in design of drugs
- Progesterone vrs. RU 486
- • RU 486 has similar structure as
- progesterone
- • It is used as an antagonist of
- progesterone in early termination of pregnancy
- Estrogen vs Tamoxifen
- • Tamoxifen has similar structure as estrogen
- • It competes with estrogen in binding to the estrogen receptor, but the tamoxifen receptor complex is inactive in gene regulation.
- The cancer cells that depend on estrogen for growth will be killed off. So tamoxifen is used in the treatment of breast cancer in humans.
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Vitamin D is derived from what?
Cholesterol
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Vitamin D is a precursor to what
Hormone essential in calcium/phosphate metabolism
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Sources of Vitamin D3
Formed in skin in reaction driven by UV light, in fish oils and as an additive in commercial milk
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Active form of Vitamin D
1,25-dihydroxycholecalciferol
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Vitamin D deficiency leads to
Defective bone formation, aka rickets
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Vitamin D formation pathway
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Eicosanoid Formation Pathway
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Functions of Eicosanoids
The inflamatory response
Regulation of pain and fever
Regulation of blood pressure
Induction of blood clotting
Control of reproductive functions
Regulation of the sleep-wake cycle
Short lived, target nearby cells
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