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Medchem 423 > Signal Transduction > Flashcards

Flashcards in Signal Transduction Deck (6)
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1. Provide examples of four types of signaling systems in the body

● Contact dependent - immune cells must contact
○ Example → immune cells

● Paracrine- wound healing cell signals close by
○ Example 1→ regulate inflammation at infection site.

● Synaptic- neurotransmitters transmit via synapse
○ Example → neurotransmitters

● Endocrine- hormone cells signal to other cells far away
○ example→ hormones


2. Describe the changes that occur in some proteins (modifications, nucleotide binding, conformational changes) that allow them to act as molecular switches.

a. Proteins act as molecular switches that converting them from an inactive (non-signaling) form to an active (signaling)

i. upstream signal induces change to enable downstream signaling


3. Be able to sketch a generic signal transduction pathway that includes a receptor, intracellular signaling proteins, and effector proteins.

see sheet for pathway:


4. Describe the molecular aspects of signaling complexes and common interaction domains, and how they provide speed and specificity in signal transduction.

a. Types of Receptors
i. Ligand-gated ion channels
1. Milliseconds
2. Ex: nicotinic ACh receptor

ii. Enzyme-coupled receptor
1. Receptor Tyrosine Kinase & SER/THR Kinases
2. Seconds to minutes
3. Ex: insulin receptor

iii. GPCRs - G Protein Coupled Receptors
1. Seconds to minutes
2. Ex: beta-adrenergic receptor

b. Interaction Domains
i. SH2 → SRC Homology 2: binds phosphotyrosine
ii. SH3 → SRC Homology 3: binds protein rich domains
iii. PTB → phosphotyrosine binding
iv. PH → Pleckstrin homology; binds phosphatidylinositol


5. Recognize the types of molecular signals (steroid) that are ligands of nuclear receptors.

● Nuclear receptors are ligand modulated proteins

● Respond to steroid hormones: cholesterol
○ Cholesterol is a major component of cell membranes,

○ hydrophobic and need carrier proteins to transport.

○ Small hydrophobic hormones can cross the membrane and then interact w/ intracellular receptors.

● respond to intracellular signals - peroxisome.


6. Describe how nuclear receptor modulator drugs can be effective even as partial agonists.

Estrogen Receptors
● Estradiol - recognizes the estrogen receptor.
- associated w/ inhibitory proteins till ligand binding allows estrogen to bind with DNA.

● Cofactors - needed to initiate gene expression

● by decreasing activity of estrogen receptor can decrease activity of estrogen receptor on cancer.

● Tamoxifen - Selective Estrogen Receptor Modulators (SERMs) is a partial agonist.
- resembles estradiol and upon its binding to estrogen receptor is causes a difference in ER activity.

- causes enough conformation change to alter activity and partially inhibit binding.