Download Signal Transduction

Signal Transduction
Cell Communication
Membrane Proteins
Cellular Communication
• Cell Junctions: Interconnect adjacent cells
• Anchoring junctions (desmosomes)
• Abundant in tissues with high stress forces (Cardiac muscles)
• Tight junctions
• Forms leak-proof sheet (Epithelial cells)
• Gap junctions & Plasmodesmata
• Direct cytoplasmic connections
• Extracellular matrix: dense mat of biomolecules
• Adhesion proteins link cells to EM
• Neurotransmitters: typically fast responses
• Hormones: long-range, often sustained, systemic actions
Initial Signals
• Chemical
• Electromagnetic
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Cations
Anions
Electrical gradient
Magnetic force field
• Pressure
• Temperature
• Another Cell
• Extracellular Matrix
• Energy
Mechanisms of Cell Signaling
• Signal molecule or physical factor from cell environment
• Internal or External environment
• Signal is “sensed” by target cell via Receptors
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Plasma membrane
Cytoplasm
Organelle
Nuclear membrane /Nucleoplasm
• Binding of ligand
• Specificity
• Agonist vs. Antagonist
• Initiate Signal Transduction Pathway
Variables of Signaling Systems
• Distance
• Neighboring cells
• Organismic
• Endurance of signal
• Seconds to hours to years
• Target cell(s)
• One or many
• Specificity
• Full molecule or merely a hapten /molecular structure
• Feedback mechanisms
• Feed-forward vs. Negative feedback
Calcium as 2nd Messenger
Role of Cholesterol
• “Good” cholesterol = high-density lipoproteins (HDL)
• >56 mg/ dL blood  60%% less Alzheimer’s cases than < 38% mg/ dL blood
• Cholesterol is major component of cell membranes
• 25% of our total cholesterol is found in brain
• Cholesterol is essential to forming connections between nerve cells
• Allows creation & retention of memories
• Glial cells supply neurons with cholesterol
• Improves rate of nerve signal transmission
• Allows neuronal connections
• Lipid rafts composed of cholesterol & receptor proteins
• Floating through plasma membrane prevents deactivation of protein
• Statins interfere with cholesterol synthesis
• May negatively affect memory in some patients