Pathology Intro

Question 1

What is pathology?

Answer 1

The study and diagnosis of disease through the examination of molecules in organs, tissues or body fluids

Question 2

What is molecular patholgy?

What is it used for?

Answer 2

• Molecular pathology is the study of molecules in a diseased state
• Molecular pathology can be used to both diagnose disease and to guid the prevention and treatment of disease. It requires an understanding of disease at a molecular level and discovery of biomarkers, in order to direct diagnosis.

Question 3

What are some of the main causes of disease?

Answer 3

• Infection→ Microorganisms (viruses, bacteria, fungi, parasites)
• Environmental→ Nutrition & Diet,Toxicity,Radiation
• Genetic→ Inherited defects,Polymorphisms

All leading to dysfunctional cells and proteins

Question 4

How are the 3 main disease causing factors be inter-related?

Draw a diagram

Answer 4

Question 5

At a molecular / cellular level, there are some key processes that can lead to disease when they happen inappropriately

Give some examples

Answer 5

• Excess cell proliferation→ Cancer and hyperplasia
• Metabolic dysfunction→Obesity, diabetes
• Excess cell death→ Neurogenerative diseases HIV
• Inflamamation and damage→ Diabetes, Cardiovascular disese

Question 6

At a molecular / cellular level, there are some key processes that can lead to disease when they happen inappropriately. How do they alter gene expression and cell behaviour?

Answer 6

Many of these processes are regulated by cell signalling pathways, which transduce signals from outside the cell, detected by receptors, via a series of proteins and 2nd messengers, to alter gene expression and hence cell behaviour.

Question 7

Explain receptor-mediated control of gene expression

Answer 7

1. A ligand, such as a growth factor, cytokine or toxin, binds to a cell surface receptor, often a G-coupled receptor or a receptor tyrosine kinase.
2. This induces receptor aggregation or a different sort of conformational change, which in turn results in association of adaptor proteins involved in signal transduction.
3. There is usually a pathway of signal transduction (e.g. mitogen-activated or stress-activated protein kinases), and this leads to activation (usually by phosphorylation either directly or indirectly) of a transcription factor.
4. This can then translocate to the nucleus and bind to its consensus sequence on the gene, leading to gene expression.

Question 8

Why is oxidative stress is a common factor in many diseases?

Answer 8

• Oxidative stress is a common factor in many diseases, especially ones involving inflammation.
• Oxidizing compounds produced during oxidative phosphorylation in mitochondria or by activated phagocytes cause chemical damage to other biomolecules, such as proteins, DNA and lipids.

Question 9

Draw a diagram to show why signalling is critical in molecular pathology

Answer 9

Question 10

Transcription Factors for Inflammation: Describe Nuclear Factor kappa B(NF-kB)

Answer 10

• This has a central role in controlling inflammation and cell survival.
• 2 related but distinct pathways exist.

Question 11

Transcription Factors for Inflammation: Describe Activator Protein-1 family (AP-1)

Answer 11

• One of the “MAP Kinase” transcription factors, which control inflammation, proliferation and cell death

Question 12

Transcription Factors for Inflammation: Describe JAK-STAT

Answer 12

• Signal Transducer and Activator of Transcription (STAT) works with Janus Kinase (JAK)
• Involved in responses to the cytokine IL-6

Question 13

Transcription Factors for Inflammation: Describe NFAT

Answer 13

• Nuclear Factor of Activated T-cells (NFAT)
• Regulates several immune processes, including T-cell development, anergy, and apoptosis. Controlled by Ca²⁺ signalling and calcineurin

Question 14

What is apoptosis?

Answer 14

Apoptosis is a regulated form of cell death that helps to control cell numbers in different situations

Question 15

How can apoptosis be initiated?

Answer 15

• Apoptosis can be initiated by the extrinsic pathway through receptor-mediated signalling.
• Apoptosis can be initiated by the intrinsic pathway, involving intracellular stress and dysfunction. Oxidative stress is one type of trigger for apoptosis.
• Both lead to caspase cascades which degrade cellular components in an organized way.

Question 16

TRUE or FALSE: Caspases are normally only activated following induction by death receptors or the apoptosome.

Answer 16

TRUE

Question 17

TRUE or FALSE: Caspases 3, 6 &7 are executioner caspases

Answer 17

TRUE

Question 18

TRUE or FALSE: Both pathways converge on caspases 3 & 7

Answer 18

FALSE

Both pathways converge on caspases 3 & 6

Question 19

Describe the extrinsic apoptotic pathway

Answer 19

1. Initiated by death receptors→Caspase-8→Caspase-3→Caspase-2+Caspase-6→Caspase-10

Question 20

Describe the intrinsic apoptotic pathway

Answer 20

Apoptosome→Caspase-7+Caspase-3→Caspase-2+Caspase-6→Caspase-10

Question 21

Describe Caspases Activation and Specificity

Answer 21

• Caspases are constitutively present in cells in an inactive form (called a zymogen).
• They are activated by proteolytic cleavage at a recognition site.
• Cleavage enables the enzymes active site to form.
• Each caspase recognizes a specific sequence of amino acids in their target substrate proteins. It has to contain an aspartate residue. Caspase-3 recognizes the sequence “DEVD”

Question 22

What can caspase activation be used to detect?

Answer 22

Caspase activation can be used to detect apoptosis: caspase-3 is a commonly used marker