Cell and Molecular Biology Exam 5

In which type of cell junction would you expect to find classical cadherins?

Adherens junctions

What type of ion regulates the homophilic interaction of cadherins?

Ca2+

Which component of adheren junctions is also an important signaling molecule within the Wnt pathway?

Beta-Catenin

True or false: 10 kDa proteins pass easily through gap junctions

false

Epithelial cells sit on a layer of....?

basal lamina

Which of the following components of ECM forms hydrated gels?

hyaluronan

When integrins are activated, which tension-sensing adaptor protein does the integrin beta chain bind to?

talin

Which of the adaptor proteins that is recruited to activated integrins directly binds to actin filaments within the cell?

vinculin

Which imaging technique could you use to detect tumors within a patient based on their unusually high uptake of radioactively labeled fluorodeoxyglucose?

PET scan

Cancer cells produce most of their ATP by...

glycolysis

True or false: Nonsense mutations are more frequently observed in tumor suppressor genes than in oncogenes.

true

True or false: In most cancers, mutation of the p53 gene is considered a passenger mutation.

false

True or false: Cells within a late stage solid tumor will be clonal, with each cell containing identical genetic changes.

false

Which of the following is difficult for cancer cells to do and acts as a barrier to metastasis?

survival in foreign tissue

What is the molecular target of the anti-cancer drug, Gleevec?

Bcr-Abl

If multiple drugs are available to treat a specific cancer, what is the most effective way to use them?

Simultaneously, as part of a mutidrug treatment regime

What term is used to describe the delivery of new (virulence) genes into bacteria by a DNA-containing virus?

transduction

What is another name for the injectosome, a structure used by pathogenic gram-negative bacteria to inject effector proteins into the cytoplasm of the host cells?

type III secretion system

What do we call the cell protrusion that forms on the surface of cells after enteropathogenic E. coli injects Tir proteins into heat cells?

pedestal

Which host cell structure is typically used to destroy ingested pathogens?

phagolysosomes

Which of the following types of cell-cell junction electrically connects cells, such as smooth muscle cells?

gap junctions
-they allow for ion exchange between cells
-found between smooth muscle cells and cardiac muscle cells

What type of cell-cell junction would you expect to find ZO proteins?

tight junctions
-ZO proteins act as scaffolds, they have multiple binding sites claudins, occludins, and other proteins and link them all together

How many repeats of the cadherin domain are found in classical cadherins?

5
(defines classical cadherins)

The hemidesmosomes and desmosomes are linked by intermediate filaments in intestinal epithelial cells. What are these intermediate filaments made of?

keratin
(desmin in heart muscle cells)
(lamins found in nucleus/ nuclear lamins)

True or false: Talin functions as a tension sensor at cell-cell junctions.

false
because it works at cell matrix junctions

Laminins are protein complexes that help to organize the basal lamina. How are they structured?

heterotrimers

Which component of extracellular matrix is highly hydrophillic and will form gels even at low concentrations?

haluornin
(collagen, fibrinectin, laminin are all proteins and will not form gels)

True or false: Collagen fibrils can expand and contract, stretch and recoil much like a rubber band.

false
this describes elastin.

Collagen molecules are mostly made up of...?

glycine, proline, and hydroxyproline

Certain proteins are referred to as tumor suppressors because...?

when their expression is decreased, cell division can increase dramatically

True or false: Nonsense mutations are more frequently observed in tumor suppressor genes they they are observed in oncogenes.

True
truncating mutations

True or false: Oncogenes function in a recessive manner.

false
typically dominant
only need one hyperactive version of an oncogene to give you the phenotype

Cancer cells produce most of the ATP by....?

glycolysis

According to the cancer stem cell hypothesis tumors contain a mix of cancer stem cells and transit amplifying cells. In what sort of ratio would you expect to find the cells in a tumor?

Most cells would be transit amplifying cells, with few cancer stem cells.
Only about 1% of a tumor can establish a new tumor if injected into another host organism.
Relatively few cells in a tumor are actually cancer stem cells

Imagine that you've developed a drug that selectively triggers apoptosis in cancer stem cells within cancer patients. What would you expect to happen to the transit amplifying cells within the tumor?

Without the cancer stem cells, the transit amplifying cells would eventually die out.
Transit amplifying cells are only able to do a few divisions by themselves before they become senescence or die, you need the cancer stem cells to maintain the bitumen.

Which of the following can act as an oncogene when overexpressed or mutated in cells?

KRas
p53 is a tumor suppressor

What are contralateral metastasis?

when cancer spreads from one organ on one side of the body to the same organ on the opposite side of the body

True or false: contralateral metastases are very common.

false

What term is used to describethe introduction of free DNA containing a gene could be a relevance factor into a bacterium ?

transformation
(free DNA)

What effect does the injection of enteropathogenic E. coli tear proteins have on host cells?

trigger pedestal formation on the surface of host cells

True or false: Only RNA viruses can have envelopes.

false
DNA viruses can have them too

Many intracellular pathogens are able to stimulate phagocytosis by host cells. What tern do we use to describe the process when the pathogen injects effectors into the host cell to stimulate the formation of protrusions around the the pathogen leading to its internalization?

trigger mechanism
-bacterium has to inject effectors and change the cytoskeleton of the host cells and get it to throw put protrusions around the bacterium.
-the zipper mechanism is when the pathogen interacts with cell surface proteins on the host cell, usually things like cadherins or intgrins and triggers endocytosis this way

True or false: In all cases, only phagocytic cells like neutrophils and macrophages are able to internalize intracellular pathogens. Non-phagocytic cells like fibroblasts can never act as hosts for intracellular pathogens.

false
the trigger or the zipper mechanism enables nonphagocytic cells to internalize pathogenic bacteria

Strong cell-cell junctions found within the intercalated disks of cardiac muscle cells and is linked to intermediate filaments within the cells

desmosomes

This junction is part of the junctional complex and is connected to the cell's actin cytoskeleton

adherens junctions

Contains 5 cadherin domains and is found at adherens junctions

Classical cadherins

Transmembrane proteins that form gap junctions

Connexins

This transmembrane protein is required for the formation of tight junctions

Claudin (the other type is occludin)

Electrically connects adjacent cells

gap junctions

Binding of which ion increases the rigidity of the hinge region of cadherin protiens?

calcium

The tension-sensitive protein within the cytosolic portion of the complex

alpha-catenin

A multifunctional protein component of adherens junctions that also acts as a transcriptional regulator

beta-catenin

The circumferential rings of actin linked to adherens junctions in epithelial cells

adhesion belts

The three main classes of ECM macromolecule

Proteoglycans and GAGs
Fibrous proteins
Glycoproteins

Forms gels even at low concentrations

Hyaluronan

The three most common amino acids in collagen proteins

glycine, proline, and hydroxyproline

At what type of structure would you expect to see fibronectin filaments form?

focal adhesions

Heterodimers that help to organize the basal lamina

Laminins

Which tissues would you expect to find associated with the basal lamina?

Usually epithelium but basal lamina is also associated with muscle fibers and is found in the kidney glomerulus

The types of junction used by cells to adhere to basal lamina

hemidesmosomes, actin-linked cell-matrix junctions

True or false: Integrins can exist in two major activity states, inactive/folded and active/extended

True

The tension-sensitive protein within the cytosolic portion of the complex

talin

A component of active integrin complexes that is also found at adherens junctions

vinculin

General term used to describe signaling events occurring within the cell that causes integrins to transition from the inactive to the active state

inside-out signaling

Normal cells vs cancer cells metabolism

Normal cells:
rate of glucose uptake: variable (low in adult tissues)
Primary method of ATP production: oxidative phosphorylation
net products of glucose metabolism: CO2, water, and energy

Cancer cells:
rate of glucose uptake: high
primary method of ATP production: glycolysis
net products of glucose metabolism: lactate, building blocks, and energy

The shift in metabolism observed in cancer cells is known as the...?

Warburg effect

Oncogenes vs Tumor suppressors

Oncogenes:
functions in normal cells: typically promote growth of cell cycle entry
missense or truncating (nonsense) mutations: missense
mutations in cancer are loss or gain in function: gain-of-funtion
expression level and/or activity in cancer cells: increased

Tumor-Suppressors:
functions in normal cells: typically inhibit growth or cell cycle entry or play a role in the maintenance of genome fidelity
missense or truncating (nonsense) mutations: truncating (nonsense)
mutations in cancer are loss or gain of function: loss-of-function
expression level and/or activity in cancer cells: decreased

Used by the gram-negative bacteria to inject effector proteins into host cells

type 3 secretion system (T3SS)

Structure that forms on the surface of host cells in response to the injection of Tir effector proteins

pedestal

Effector protein used by Listeria to escape the phagosome

Listerolysin

Name one of the 3 pathogens discussed in the course that moves around the host cells by polymerizing actin

Listeria monocytogenes
Shigella flexneri
Rickettsia rickettsii

Name the pathogen that replicates within a vacuole that resembles the rough ER

legionella pneumonia

Name the pathogen that replicates within the late endosomes

samonella enterica