Vesicular Trafficking II Flashcards
What are some examples of Acid Hydrolases found within a lysosome?
nucleases, proteases, glycosidases, lipases, phosphotases
What is the pH of Acid Hydrolases?
pH of around 5.0
Lysosomes require an ___ environment and ___ cleavage for optimal activation
acid; proteolytic
True or False?
Vacuolar ATPase pumps H+ into lysosomes to maintain the acidic pH and to drive transport of small metabolites
true
What are some of the multiple pathways used to deliver materials to lysosomes?
phagocytosis - phagosome - lysosome
endocytosis - early endosome - late endosome - lysosome
macropinocytosis - late endosome - lysosome
endocytosis/macropinocytosis - autophagy - autophagosome - lysosome
In regards to sorting of lysosomal proteins, lysosomal hydrolases have mannose-6-phosphate attached to them in the what?
CGN
In regards to sorting of lysosomal proteins, M6P receptors in TGN recognize what?
the sugar on the lysosomal protein
In regards to sorting of lysosomal proteins, clathrin-coated vesicles that bud from the TGN are delivered into ___ and then to ___
endosomes; lysosomes
What causes Hurler’s Disease, a type of lysosomal storage disease?
mutation in the enzyme required to break down glycosaminoglycan chains
What causes Inclusion Cell disease, a type of lysosomal storage disease?
all of the lysosomal hydrolyses are missing in fibroblasts
When there is a defective or missing GIcNAc phosphotransferase (an enzyme that adds M6P to lysosomal hydrolyses, what happens?
the enzymes are not phosphorylated and hence not sorted into vesicles and not delivered into lysosomes, they are instead secreted into blood
True or False?
An example of receptor-mediated endocytosis is cholesterol uptake
true
Receptor-mediated endocytosis provides what type of mechanism?
selective concentration mechanism
How does endocytosis of cholesterol work?
endocytosis of clathrin coated vesicle containing LDL molecule and LDL receptor. Uncoating of the vesicle leads to fusion with an endosome (early endosome). Part of endosome with LDL receptor buds off and is transported back to plasma membrane. The other part of the endosome (late endosome) containing the LDL molecule is taken to a lysosome where it is broken down to free cholesterol
What is the role of the clathrin-coated pit in cholesterol uptake?
to accumulate LDL receptors
Pinocytosis or cell drinking is a ___ process that occurs continuously in all eukaryotic cells.
consitutive
The process of Pinocytosis occurs where?
clathrin coated pits
In regards to pinocytosis thorugh clathrin coated pits, the membrane invaginated and pinches off to form calthrin coated vesicle. This vesicle contains ___ fluid with various solutes trapped in pits as they invaginate
extracellular
Flask shaped invaginations are called what?
caveolae
What are caveolae enriched in?
cholesterol and glycosphingolypids and GPI-anchored membrane proteins
What is the major structural protein of Caveolae?
caveolin
How does pinocytosis through caveolae work?
caveolae invaginate into membrane by virtue of lipid composition and not the protein coat, they then pinch off from PM by dynamic and form a caveosome
Do caveolae connect with lysosomes?
no
Transport vesicle move from TGN to plasma membrane. The fusion of vesicles with the plasma membrane is called what?
exocytsosis
This secretory pathway of exocytosis operates continously
constitutive pathway
This secretory pathway of exocytosis is triggered by signals (hormones or NTs)
regulated pathway
In terms of protein sorting in the TGN. There are 3 patwhays a protein can go.. What are they?
Signal mediated to lysosome
Constitutive to PM
Signal mediated to secretory vesicles and then to PM for regulated secretion
