Cell biology IV Flashcards
What protein is involved in constructing and shaping of the sER?
Atlastin
What class of protein is atlastin?
GTPase
What happens to the ER and Golgi in response to an abundance of atlastin?
1) Increased ER membrane fusion2) Absence of Golgi
What happens to the ER as a result of atlastin deficiency?
ER fragmentation
ER fragmentation occurs in response to a deficiency in what protein?
Atlastin
Hereditary spastic paraplegia is caused from a deficiency in what protein?
Atlastin
What condition arises due to atlastin deficiency?
Hereditary spastic paraplegia
What are symptoms of hereditary spastic paraplegia?
1) Leg stiffness2) Gait disturbances (stumbling, tripping)
Proteasomes make up what percentage of cellular proteins?
1%
Are proteases ATP-dependent?
Yes
Where are proteasomes located in the cell?
Cytoplasm and nucleus
Proteasomes are involved in proteolysis of what types of proteins?
1) Regulating proteins (e.g. cell cycle, txn, apoptosis)2) Malformed, denatured, damaged proteins3) Antigenic proteins (cleaved and presented to T cells)
Are proteasomes ubiquitin-dependent, -independent, or both?
Can be either (both)
Proteasomes are inhibited by what type of molecule?
Abnormal prion proteins
What effect to abnormal prion proteins have on proteasomes?
Inhibition
Defective proteolysis by proteasomes is causative in what diseases?
Parkinson’s disease, cystic fibrosis
What is the function of bortezomib in cancer cell therapy?
Bortezomib partially inhibits proteasomes, thus decreasing the degradation of pro-apoptotic factors
In polarized cells, where is the Golgi located?
Between the nucleus and apical cytoplasm
When is a negative Golgi image seen?
In active protein-secreting cells
What is a negative Golgi image?
A pale-staining area of cytoplasm seen in H&E staining (neither acidophilic nor basophilic)
In which direction is the cis-Golgi oriented in the cell?
Presents toward the transitional ER where transport vesicles are forming
What is formed from the trans-Golgi?
1) Secretory granules (vesicles)2) Lysosomes3) Membrane protein-transporting vesicles
Where are lysosomal enzymes tagged with mannose-6-phosphate?
Golgi
Where is the mutation in Wilson’s disease?
Mutation in a protein pump for copper in the trans-Golgi network of liver cells
What is the result of the mutated protein transporter in Wilson’s disease?
Impaired biliary excretion of copper
What is the role of dysferlin?
Repair of microperforations in skeletal muscle plasma membranes
Repair of microperforations in skeletal muscle plasma membranes is accomplished by what molecule?
Dysferlin
The patching mechanism of dysferlin is dependent upon what mineral?
Calcium
Mutations of the dysferlin gene lead to what three types of muscular dystrophy?
1) Miyoshi myopathy2) Limb-girdle muscular dystrophy type 2b3) Distal myopathy tibialis anterior muscle onset
How does a mutation in proinsulin lead to proinsulinemia?
1) Mutated proinsulin is missorted into the unregulated (constitutive) secretory pathway2) Prohormone converting enzymes are properly sorted in the regulated pathway3) Consequently, there is an absence of prohormone converting enzyme activity in the unregulated pathway
What are the four types of endosomal compartments?
1) Early endosomes2) Recycling endosomes3) Multivesicular bodies4) Late endosomes
Where are early endosomes and recycling endosomes located in the cell?
Periphery
Which endosomal compartments are located at the periphery of the cell?
Early endosomes, recycling endosomes
What is the pH of early endosomes and recycling endosomes?
6.2 - 6.5
Which endosomal compartments have a pH of 6.2 - 6.5?
Early endosomes, recycling endosomes
Which endosomal compartment is responsible for glucose transport in response to insulin?
Recyling endosome
What is the pH inside multivesicular bodies?
5.0 - 6.2
Which endosomal compartment has a pH of 5.0 - 6.2?
Multivesicular bodies
What do multivesicular bodies eventually fuse with?
Late endosomes
Do multivesicular bodies have a secretory role?
Yes
Where are late endosomes located in the cell?
Near Golgi and nucleus
Late endosomes either fuse or mature into _______
Lysosomes
What is another term for late endosomes?
Prelysosomes
What is the pH of late endosomes?
5.0
Which endosomal compartment has a pH around 5.0?
Late endosome
What are the four fates of receptor-ligand complexes?
1) Receptor is recycled, ligand is degraded or released for use (e.g. LDLr)2) Receptor and ligand are recycled (e.g. TfR)3) Receptor and ligand are degraded (e.g. FGFR3 - reverse occurs, leading to achondroplasia)4) Receptor and ligand are transported across cell and secreted (transcytosis, e.g. antibodies in glandular cells)
What do lysosomes transport?
Lysosomal hydrolases and other ions and molecules
In which cell type are lysosomes most abundant?
Phagocytic cells (macrophages, neutrophils)
What is an autophagolysosome (secondary lysosome)?
Primary lysosome + autophagosome
Primary lysosome + autophagosome = ?
Autophagolysosome (secondary lysosome)
What is a heterophagolysosome?
Primary lysosome + heterophagosome
Primary lysosome + heterophagosome = ?
Heterophagolysosome
What are residual bodies?
Lysosomes that contain undigested waste
Accumulated waste in residual bodies eventually forms what inclusion?
Lipofuscin
Are lysosomes acidophilic or basophilic?
Acidophilic
