Download Outline Section 4

IV. Lecture Section 4
A. Review of signaling system organization
1. Basic Ideas
a. Communications between two cells in a multicellular organism
b. Four components to all signaling systems
2. Ligands and their sources
a. Fluid dispersed: Endocrine, Paracrine, Synaptic, Cytosol Exchange
b. Iimmobilized ligands: Cell-to-cell signals, Matrix-to-cell signals
3. Receptors, second messenger cascades and target mechanisms
a. Transmembrane plasmamembrane receptors
b. Intracellular receptors
c. Intracellular second messenger cascades
d. One or more target mechanisms
B. Consensus signal pathways and molecules (Chapter 15)
1. Classic signal transduction pathways
a. G-protein linked receptor --- G-protein --- adenyl cyclase
b. G-protein linked receptor --- G-protein --- phospholipase C
c. Receptor tyrosine kinase --- ras --- MAPK
d. Receptor serine-threonine kinase --- SMAD --- gli protein
e. Cytokine receptor --- JAK --- STAT
f. Inhibitor inhibition pathways: Hedgehog, Wnt, thrombin-PPAR
g. Multicellularity and cell communication evolved independently in
plants and animals
C. Integration, heirarchy and regulation by multiple required signals (Chapter 15)
1. Specialization in the ligand-receptor interaction
a. Specialization: Ligand-Receptor affinity and rate of turnover
b. Integration: Cells are exposed to hundreds of signals but gene
expression hardwires them to respond to a subset of signals
2. Single target mechanism pathways and convergent crosstalk
a. When a hardwired target mechanism is achieved in absence of ligand
b. Convergent, or redundant, cross-talk for essential responses occurs
when two or more ligands can produce the same target mechanism
3. Multiple target mechanism pathways and divergent crosstalk
a. Divergent cross-talk for complex, integrated responses where a single
ligand can activate two or more systems
4. Many complex functions vary by the combinations of signals present
a. Types of actions include neuron action potentials, cell division and
immune cell activation
b. Mechanisms of action include summation of ion movements at
plasmamembrane, transcription factor expression in the nucleus and
combined cytosolic and nuclear activation
c. Multiple signals also subject to heirarchical considerations/relationships
D. Signal pathway structure depends on desired function; Example: muscle
contraction
1. The contractile filaments of all muscle types are organized in much the same
way but all come from different genes
2. Contractile regulation of skeletal muscle is designed to produce voluntary, allor-nothing contractions of great power but subject to fatigability
3. Contractile regulation of cardiac muscle is designed to produce involuntary, allor-nothing contractions of moderate power but not subject to fatigability
4. Contractile regulation of smooth muscle is designed to produce involuntary,
continuum contractions of low power but not subject to fatigability
5. How might the waving of cilia and flagella be similar
E. Cellular Movement (Chapter 16, 25)
1. Review of the Fundamental Structures and Functions involved with Movement
a. What cells move?
b. What causes them to move?
c. What strategies do they employ?
2. Regulation of the Movement of Cells and Organisms Reflect the Different
Evolved Activities of those Organisms but the Fundamental Mechanisms are
Often Conserved
a. Many prokaryotic cells have a structure composed of a membranebound motor complex driving propeller-like movement of the extracellular
flagellum
1. The helical structure of flagellin allows for two kinds of
movement: coordinated linear vs. stationary ‘tumbling’
2. Receptor-mediated regulation of flagellum activity results in the
signal controlling movement and not the prokaryote
b. Ciliar and flagellar eukaryotes
1. The basic mechanism
2. Cells that swim vs. stationary cells in animals
3. Microtubular structure and function
c. Cell crawling
1. The basic mechanism
2. Actin treadmilling and migratory platform movement
3. Attachment and myosin-mediated cell traction
4. Participation of other cellular components
5. Extravasation of WBC from the animal vasculature
d. Cell Shortening and muscular movements
e. Movements in plants