Triana Flashcards
What are some examples of microtubule-mediated movement within cells?
Translocation of ER toward the (+) end of microtubules.
Dynein-based transport from ERGIC to the cis-Golgi.
Membrane budding from the trans-Golgi network (TGN) via actin.
Kinesin-based transport from the TGN to the periphery.
Actin involvement in ER-to-Golgi movement of vesicles/tubules.
What are the primary functions of microtubules?
Microtubules provide structural support and serve as tracks for ATP-powered motor protein movement (e.g., dynein, kinesin) for cargo transport.
They are essential for forming the mitotic spindle during cell division.
Microtubules provide an organizational framework for cell substructure and serve structural roles in cilia and flagella.
Microtubules require GTP hydrolysis to regulate their dynamics.
How do specific toxins affect microtubules?
Taxol stabilizes microtubules and inhibits depolymerization—useful for studying microtubule dynamics.
Colchicine and nocodazole inhibit polymerization of microtubules—used in research to disrupt microtubule formation.
What are the functions of intermediate filaments?
Intermediate filaments have greater tensile strength than actin microfilaments or microtubules.
They provide structural integrity in tissues and stabilize the nuclear membrane.
Intermediate filaments contribute to barrier functions in the skin and structural roles in hair and nails.
Unlike microtubules and actin filaments, intermediate filaments lack polarity and do not serve as tracks for intracellular movement.
What are some of the key functions of peroxisomes?
Bile acid synthesis
Ether lipid synthesis
Detoxification of ROS (Reactive Oxygen Species)
D-amino acid oxidation
Fatty acid oxidation
How are peroxisomes involved in neuronal development?
Peroxisomes play a critical role in neuronal development, including processes such as lipid metabolism and detoxification necessary for proper cell function.
What is Refsum disease and how is it related to peroxisomes?
Refsum disease is a rare disorder caused by the inability to metabolize phytanic acid, leading to its accumulation.
It results from mutations in peroxisomal enzymes like PHYH, which metabolize phytanic acid.
Symptoms include:
Ophthalmologic issues (vision loss)
Neurologic issues (hearing loss)
Ataxia
Skeletomuscular abnormalities
Other diverse symptoms.
How do we identify specific organelles in cells?
Organelle markers: Use quantitative confocal microscopy.
Example: ER uses an ER localisation signal fused to red fluorescent protein mCherry.
Example: Peroxisomes use a peroxisome targeting sequence (PTS) fused to GFP.
Cell fractionation:
Cell homogenisation to gently lyse the plasma membrane.
Differential centrifugation or gradient centrifugation to separate organelles.
Use Polyacrylamide gel electrophoresis (PAGE) and Western blotting to detect specific proteins.
What is mitochondrial fission and its significance?
Mitochondrial fission is the process of a mitochondrion dividing into two.
It plays roles in:
Inheritance and partitioning of mitochondria during cell division.
Proper distribution of mitochondria.
Release of cytochrome C during apoptosis.
How do new Golgi structures form according to the de novo formation model?
The de novo formation model suggests that new Golgi structures arise independently of existing ones.
New structures are formed using materials that come from the ER.
What does peroxisome biogenesis involve?
Peroxisome biogenesis encompasses the formation of peroxisomal membranes, the import of matrix proteins, and the proliferation and inheritance of peroxisomes.
How do organelles communicate with each other?
Organelles communicate via membrane contact sites (MCSs), which are functional close contacts between organelles.
These contact sites play roles in:
Intracellular signaling
Lipid metabolism
Motor-protein-mediated membrane dynamics
Organelle division
Organelle biogenesis
What are membrane contact sites (MCSs)?
Membrane contact sites are locations where two organelles are close enough together to be tethered by molecular machineries, typically within 30-50 nm, but sometimes more. The organelles at MCSs do not fuse.
What is the function of tethers at MCSs?
Protein complexes, called tethers, hold organelles together at MCSs. These complexes can insert into the organelles or bind to proteins or lipids in the opposing membranes. They often have additional functions beyond just physical tethering.
Are MCSs static or dynamic?
MCSs are dynamic; they can be induced, split, and induced again, regulating various cellular processes.
What is the role of the lysosome-peroxisome MCS?
The lysosome-peroxisome MCS regulates the transfer of cholesterol between the lysosomes and peroxisomes. This process involves several key proteins and tethering mechanisms.
What are the key proteins involved in the lysosome-peroxisome MCS?
Synaptotagmin VII (Syt7): A lysosomal protein that binds to peroxisomes.
Syt7 binds PI(4,5)P2, helping to tether peroxisomes to lysosomes.
What is the role of ACBD5 and ACBD4 in cholesterol transport?
ACBD5 (and ACBD4) are transmembrane peroxisomal proteins involved in cholesterol metabolism. They participate in lipid transfer at the ER-peroxisome MCS by interacting with VAPB and VAPA, which are ER proteins.
How is cholesterol metabolized and transported in cells?
Cholesterol is taken up from the blood and accumulates in lysosomes. The cholesterol is then transferred from the lysosomes to the peroxisomes via the MCS for further processing.
What happens if cholesterol metabolism is disrupted?
If cholesterol transport between the organelles is disrupted, cholesterol accumulates in the lysosomes, leading to various neurological defects and lysosome storage disorders.
What happens when lysosome-peroxisome MCSs malfunction?
Dysfunction in lysosome-peroxisome MCSs leads to cholesterol accumulation in lysosomes and can result in neurological defects, contributing to lysosome storage disorders, where lysosomes cannot properly process and distribute their contents.
What is the consequence of dysfunctional ER-peroxisome MCSs?
Dysfunction of ACBD5-VAPB contacts in the ER-peroxisome MCS leads to decreased plasmalogen synthesis and reduced overall cholesterol production.
How are MCSs hijacked by bacteria and viruses?
Bacterial and viral proteins often interact with VAP at MCSs. These contacts are critical for viral replication and the hijacking of cellular functions during infection.
How are MCSs defined in microscopy?
MCSs are areas of close apposition (30 nm) between the membranes of two organelles that serve a specific function. These sites can be studied with Electron Microscopy (EM), which provides atomic-resolution imaging.
What does Electron Microscopy (EM) reveal about MCSs?
EM provides high-resolution ultrastructure information and allows for measurement of the distance between organelles at the contact sites, revealing their close proximity.
