Lipid Signaling Flashcards
What is the structure of the plasma membrane?
-polar head group
-fatty acid tails
phospholipid
Which type of phospholipid makes up the plasma membrane?
glycerophospholipids
What is a phospholipase?
Hydrolyzes phospholipids
What does the phospholipase C reaction do?
PIP2 (an important effector) through PLC splits into two molecules; DAG and IP3, which are important second messengers
What hormones stimulate PLC?
-alpha1-adrenergic
-TRH
-dopamine
-vasopressin
-angiotensin II
What processes are regulated by PLC activation?
-glycogen breakdown
-amylase secretion
-insulin secretion
-smooth muscle contraction
-platelet aggregation
-fluid secretion
What is cyclic GMP?
-synthesized by receptor guanylate cyclases
-degraded by cGMP phosphodiesterases
What is receptor guanylate cyclases and what are the two types?
-provide cyclic GMP
-cyclic GMP activates protein kinase G
-two types:
Cell surface- activated by extracellular signals
Intracellular- activated by NO produced by nitric oxide synthase which induces vasodilation
How does Viagara work?
Inhibits certain isoforms of cGMP phosphodiesterase
What is a receptor tyrosine kinase?
-plasma membrane receptors that are also enzymes
ex insulin receptor or epidermal growth factor receptor
What does each alpha or beta subunit of the insulin receptor contain?
alpha- cysteine-rich insulin binding region
beta- tyrosine kinase domain
both are joined by disulfide bonds
Explain the activation of the insulin receptor?
Autophosphorylation;
-insulin binds
-Beta phosphorylates itself
-can then phosphorylate other things
What are the 2 actions of insulin?
P13 kinase pathway- metabolic actions
MAP kinase pathway- mitogenic actions
Explain insulin stimulation of glucose transport in muscle and fat.
Without insulin, transports on on intracellular vesicles. When insulin is added, transporters migrate from intracellular vesicles to plasma membrane.
What is desensitization?
prolonged exposure to a signal often results in desensitization.
