Exam #1; Cell Biology II Flashcards
Peripheral Protein
- Attached to the extracellular side of the plasmalemma
- Can be removed w/ salt solution
Integral Protein
Protein partially or fully embedded in the plasmalemma
Transmembrane Protein
Proteins that extend through the entire thickness of the plasmalemma
Beta-Amyloid Precursor Protein (B-APP)
- Integral transmembrane protein
- Abnormal cleavage forms Beta-Amyloid peptides that aggregate
- Protein aggregates are resistant to proteolysis and implicated in Alzheimer’s Disease
Normal Function of B-APP
- Neuronal migration during development
- Synaptic formation & repair
- Cell signaling
- LTP (memory)
- Cell adhesion
PrP
- Prion Protein
- GPI anchored protein
- GPI anchor is embedded in lipid rafts
- Mutation implicated in Creutzfeld-Jakob Disease
Normal Function of PrP
- Neuroprotection against ischemia
- Control circadian rhythm
- Organization of myelin sheath
What stain can be used to visualize Beta-Amyloid & PrP?
Congo Red
What are the seven functions of proteins?
1) Receptors
2) Carriers/ Pumps/ Channels
3) Enzymes
4) Linker proteins for structural support
5) Antigens (cell id. tag)
6) Anchor cell to ECM
7) Intercellular junction complexes
What does it mean that receptors are dynamic and not static?
- There is up & down regulation of receptors in response to ligand to maintain homeostasis
- Decrease Ligand: Increase Receptor
- Increase Ligand: Decrease Receptor
How do pharmacologic agents act to produce a therapeutic effect?
As receptor agonists or antagonists
What is the clinical relevance of estrogen receptor?
- Many breast cancers show an upregulation of estrogen receptors
- ER + breast cancer can be treated with Tamoxifen/ Hormone Therapy
Transport Proteins
- Carriers
- Pumps
Carriers
- Transports without direct expenditure of energy
Pumps
- Transport with direct expenditure of energy
Na+/K+ Pump
- 3 Na+ Out & 2 K+ In w/ ATP energy
- Regulates intracellular volume
Digoxin
- Used to treat heart failure
- Partially inhibits Na+/K+ Pump, which leads to an increase in Na+ concentration in the cell
- Destroys the concentration gradient needed for the Ca++/Na+ transporter
- Increases sarcoplasmic Ca++
- Increased sarcoplasmic Ca++, increases cardiac contractility
Ca++/Na+ Transporter
- 4 Na+ In & 1 Ca++ Out
-
Secondary Active Transport
Coupling the movement of a molecule down its concentration gradient to the electrochemical gradient established by primary active transport i.e. a pump
Na+ & Glucose Co-transport
- Example of secondary active transport
- Glucose & Na+ transported into the cell down concentration gradient
- Na+/K+ Pump uses ATP energy to established this concentration gradient
Multi-drug Resistant Transporters
- Subfamily of primary transporter proteins that are ATPases
- Transport molecules out of the cell
MDR-1
- Transports drugs out of the cell
- Overexpression can cause cancer cells to become resistant to cytotoxic drugs; they;re transported out of the cell too quickly to take effect
MDR Treatment
- RNA interference: silencing the gene coding for the MDR transporter
- Pharmacologic Inhibition
MDR-2
Transports conjugated bilirubin from the hepatocyte into bile canaliculus
Dubin-Johnson Syndrome
Benign disorder caused by a mutation in ATP binding region of MDR-2
Aquaporin
Protein channel for water
Aquaporin-2
Expressed by renal collecting tubule for water reabsorption
ADH & Vasopressin
- Cause translocation of aquaporin receptors into the plasma membrane of the renal collecting tubule cell
- Increase water reabsorption through the kidney
CFTR
- Chloride channel implicated in cystic fibrosis that also regulates Na+ & HCO3-
- Causes salty sweat
- Dehydrated airway mucous leading to chronic airway infection
Lactose Intolerance
- Decrease in lactase enzyme
- Lactose is not absorbed; rather, interacts with gut flora
- Causes gas, bloating, diarrhea
Linker Protein
- Links plasma membrane to underlying cytoskeleton
Dystroglycan
- Linker protein in skeletal muscle that links cytoskeleton to plasma membrane
- Binds Dystrophin, a protein of the cytoskeleton lacking is Muscular Dystrophy
Glycolipid
Carbohydrate attached to lipid
Glycoprotein
Carbohydrate attached to protein
Ganglioside Gm1
- A glycolipid that serves as the receptor for cholera toxin
Cholera Toxin Mechanism
- Binds Ganglioside Gm1
- Increases cAMP
- cAMP causes Cl- efflux from CFTR
- Cl- efflux causes Ha+ & HCO3- efflux
- Causes profound diarrhea
What are the 5 pathways of endocytosis?
1) Macropinocytosis
2) Clathrin-Mediated Endocytosis
3) Non-coated-mediated endocytosis
4) Caveolae-mediated endocytosis
5) Phagocytosis
Creutzfeld-Jakob Disease
- Prion Disease caused by conversion of PP into PrP
- “human mad cow disease”
