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Histopathology > Cell Communication > Flashcards

Cell Communication Flashcards

1
Q

What is the function of junction in cell

A

Provides mechanical link between cells.

Enables cell receptors to recognise ligand of other cells

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2
Q

Types of cell junction

A

Anchoring jxn
Occluding jxn (tight)
Communicating jxn(gap)

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3
Q

Examples of anchoring Jxns

A

Hemidesmosomes
Desmosomes
Adhering jxnz

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4
Q

Name the junction that forms junctional complexes

A

Tight Junction ( Zonula occludens)
Desmosomes (macula adherens)
Adhering jxn (Zonula adherens)

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5
Q

What are fxns of occluding cells

A

They bind adjacent cells by forming a tight mesh like network of macromolecules btw them.

Prevent paracellular communication btw cells.

They maintain cell polarity by segregating apical and basolateral domain of cells.

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6
Q

Name the transmembrane proteins that mediate this cell to cell interaction in Zonula occludens

A

Occludin
Claudin
Zonulin
Catenin

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7
Q

Are tight junctions permanent structures?

A

No!
They degrade in respect to proliferation and migration

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8
Q

Anchoring junction;

A

They attach cells and their intracellular cytoskeleton to another cell or extracellular space.

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9
Q

When cell is attached to another cell in anchoring Jxns it is known as

A

Spot desmosomes

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10
Q

When cell is attached to extracellular matrix in anchoring Jxns it is known as;

A

Hemidesmosomes.

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11
Q

Adherence has two types of focus

A

Small and Broad;

Small; Spot desmosomes and hemidesmosomes

Broad band ; belt desmosomes

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12
Q

Transmembrane proteins associated with cell to cell interaction in desmosomes is called;

A

Cadherin;
It attaches to intermediate filament (I.C cytoskeleton)

Cadherin are made up of two proteins; Desmoglein and Desmocolin

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13
Q

The importance of the linkage with intracellular cytoskeleton is to?

A

Allow mechanical force to be dessipate over multiple cells.

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14
Q

Belt desmosome protein

A

Known as E-cadherin attach to an actin filaments (IC cytoskeleton)

This attachment influence cell shape and motility.

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15
Q

Transmembrane protein in hemidesmosomes;

A

Connectin also known as intergrin

It attaches to intermediate filament (IC cytoskeleton)

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16
Q

Importance of focal adhesion complex

A

It plays a role in cell signalling.

Eg: greater than 100 proteins localized in hemidesmosomes can generate intracellular signals when the cell is under stress

E.g seen in endothelium and myocytes of failing heart.

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17
Q

Importance of Gap junctions

A

Mediates passage of chemicals and electrical signals from one cell to another.

It also facilitates cardiac myocyte to fxn as a syncytium.

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18
Q

Transmembrane protein of Gap junction

A

A hexamer called CONNECXINS.

Has a pore of 1.5-2nm called CONNEXONS

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19
Q

Molecules that pass through gap junctions

A

Ions
Nucleotides
Amino acids
Vitamins
Carbohydrates(sugar)
Vitamins
And small molecules.

20
Q

Factors that affect permeability of Gap junction

A

Decrease PH
And Hypercalcaemia.

21
Q

What are signals ?

A

Biological commands to cell that influence their life or death, quiescence or stimulates their specific functions

22
Q

Where can cell communication (signals) come from?

A

Intracellular or extracellular signals

23
Q

Groups of cell signals;

A
  1. Signal to exert damage to neighbouring cells
  2. Contact with neighbouring cells
  3. Contact with ECM
  4. Signal to secrete substance’s e.g growth factors, cytokines and hormones.
24
Q

Types of cell signalling based in distance of signal function

A

Paracrine
Autocrine
Synaptic signalling
Endocrine signalling.

25
Q

What is paracrine signalling;

A

Cells and target cell are in close vicinity

26
Q

Autocrine signalling;

A

Molecules secreted by cell affects same cell.
Response can be amplified.
Response can also undergo feedback inhibition.

27
Q

Synaptic signalling;

A

Occurs at specialized cell junction known as synapses.

Mediated by NTRansmiter secreted by activated neuron unto to target cell.

28
Q

Endocrine signalling

A

Mediator is released into the bloodstream and target cell is far from the release cell

29
Q

What is signal transduction:

A

Is the transmission of these biological commands to achieve desired cell functions

30
Q

Receptors?

A

Are proteins to which ligands binds to activate cascade of intracellular events that culminate into desired cell response

31
Q

Intracellular receptor:

A

Are transcription factors that are activated by lipid soluble ligands that cross plasma membrane.

32
Q

Cell surface receptors

A

Transmembrane proteins with intracellular and extracellular domains.

IC domain binds ligands

EC domain initiate cascade of events.

33
Q

Ligand binding effect on cells;

A

1) open ion channels seen in synapses.
2)Activate G-protein coupled receptor.
3) Activate tyrosine kinase.

4) trigger proteolytic events or change protein binding stability that activates a latent transcription factor.

34
Q

Which ligand binding effect is associated with growth factor signalling

A

G protein activation and endogenous tyrosine kinase activation.

35
Q

Which ligand effect is associated with NOTCH, WNT and hedgehog pathway.

A

The activation of proteolytic activity or change in protein binding stability that activates latent transcription factor

36
Q

Features of signal transduction include;

A

Ligands
Receptors
Second messengers
Protein phosphorylation
Amplification

37
Q

Ligands ;

A

Carry biological signals to receptors

38
Q

Second messagers

A

Signalling molecule generated on ligand receptor Interactions.

39
Q

Examples of second messengers

A

Diacylglycerol
1,4,5 inositol triphosphate
Nitric oxide.
Calcium ion
champ
cAMP

40
Q

Importance of protein phosphorylation

A

To activate inactive enzymes and proteins
Core enzyme needed is protein kinase

41
Q

Transduction can result in;

A

Immediate Change in metabolism of cell;

Immediate change in electrical charge across plasma membrane.

Change in gene expression and transcription in nucleus.. takes longer time

42
Q

Example of intracellular receptor:

A

Steroid receptor and Nitric oxide receptor

43
Q

Where are steroid receptors found

A

In the nucleus except glucocorticoid receptors seen in the cytoplasm

44
Q

What exactly is a steroid receptor

A

They’re dimer of zinc finger protein that reside in the nucleus.

This zinc finger is a DNA binding domain for transcription factors.

Steroid receptors bind to histone deacetylase keeping expression in that area depressed

45
Q

What happened when ligand binds to steroid receptor in the nucleus

A

2) the ligand steroid complex bind at the specific DNA sequence steroid response element (SRE) in the promoter that will turn it on

1) it causes the release of histone deacetylase and replace it with histone acetylases thus relieving chromosome depression.

46
Q

How does NO receptor pathway work?

A

1)It diffuse into the cell.
2) Binds to its receptor protein in the cytoplasm.
>Area of binding could be at the metal or S unit of the protein.(S as seen in cysteine)

3) This binding causes allosteric modifications an activates a second messenger.
>As seen in guanyly cyclase undergoing allosteric modifications to get activate in order to catalyse cGMP formation from cGTP

47
Q

Can NO act as both paracrine and autocrine?

A

Yes Aunty!

Histopathology (1 decks)

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