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Medicine Year 1 Semester 1 > Cell Adhesion and the Extracellular Matrix > Flashcards

Cell Adhesion and the Extracellular Matrix Flashcards

1
Q

What is the extracellular matrix ?

A

The environment surrounding cells, which varies between tissues.

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2
Q

What are the 3 major molecules involved in the ECM ?

A

Adhesive proteins
Structural proteins
Proteoglycans

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3
Q

Adhesive proteins

A

Adhere cells together
e.g. cadherins, integrins

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4
Q

Structural proteins

A

Gives tissues tensile, compressive strength.
- Collagen
- Elastin
- Keratin

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5
Q

Collagen function

A

Resists tension and can stretch

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6
Q

Elastin function

A

Elastic, returns tissue back to its original shape.

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7
Q

Keratin function

A

Tough, found in hair and nails

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8
Q

Proteoglycans

A

Fills space between cells, hydrates and cushions cells.
Consists of a protein core with sugar chains
Has a glue like function

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9
Q

How is collagen produced ?

A

Procollagen
Tropocollagen
Collagen fibrils
Collagen fibre

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10
Q

What is the loose connective tissues beneath the basement membrane of the epithelia majorly composed of ?

A

The ECM where fibroblasts are distributed.

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11
Q

Fibroblasts

A

Synthesise and secrete fibrillar proteins - collagen & elastin, as well as proteoglycans that help maintain the cell structural framework.

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12
Q

What is the major structural protein of the ECM ?

A

Collagen

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13
Q

Characteristics of collagen

A

Made of triple helix
Glycine, Proline and Hydroxyproline

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14
Q

What are the 4 types of collagen ?

A

Type (1) - Bone, Skin, Tendon
Type (2) - Cartilage
Type (3) - Reticulin, Blood Vessels
Type (4) - Basement membrane

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15
Q

What is the most abundant form of collagen ?

A

Type 1, which is one of the fibril forming collagens

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16
Q

Type 4 collagen

A

Network forming collagen
Major constituent of the basal laminae

17
Q

What is the difference between type 1 and 4 ?

A

Type 4 Gly-X-Y is disrupted by a non helical short sequence. This gives it more flexibility.

18
Q

What do adhesion proteins form interactions between ?

A

Collagen and proteoglycans

19
Q

Fibronectin

A

Main adhesion protein in connective tissues.
Made of 2 polypeptide chains

20
Q

Laminin

A

Main distinct adhesion protein in basal laminae

21
Q

Myofibroblasts

A

Bi-functional
1. Fibroblast like as they secrete collagen
2. Smooth muscle-like (synthesise actin, myosin and desmin)

22
Q

Action of myo-fibroblasts

A

Proliferate
Secrete collagen - SCAFFOLD
Consolidate damaged area - FIBROUS SCAR
Contract

23
Q

Adipocytes

A

White fat cells

24
Q

Function of adipocytes

A

Insulation
Packing - energy store

25
Q

Describe the molecular defect in Duchenne Muscular Dystrophy

A

DMD is caused by changes (mutations) of the DMD gene on the X chromosome.

Mutation of the DMD gene will result in absence of the dystrophin protein, leading to degeneration of muscle fibres.

The body can replace (regenerate) some muscle fibers, but over time more and more muscle fiber is lost.

26
Q

Recent experimental approaches to attempt to correct defect in DMD

A

Experimental drug PTC 124 (ataluren)- thought to override premature stop signal mutation to produce normal dystrophin

27
Q

What happens during cancer progression ?

A

During cancer progression, cells lose their original tissue contacts, move through the extracellular matrix (ECM), enter into the lymphatic and/or blood system, extravasate, and ultimately form new tumors.

28
Q

Carcinoma in situ

A

Carcinoma in situ refers to a group of abnormal cells that have not spread from the location where they first formed.

29
Q

Cancer progression initial stages

A

Tumour cells accumulate
Cells have not yet breached the basal lamina
Cells undergo epithelial to mesenchymal transition.

30
Q

Cancer progression - micro-invasion

A

Cells convert to ‘mesenchymal cells’ and the expression of cadherins is reduced

Micro-invasion starts sided by INVADIPODIA.

Secretion of MMP’s

Basement membrane breached

In invading tumours, leading cells express integrins, promoting interaction with the ECM and non-epithelial cells.

31
Q

Cancer progression to metastasis

A

Autocrine motility factors form tumour.

Angiogenesis factors

Entry into and through lymphatic and blood vessels.

Dissemination - metastatis

32
Q

Metastasis

A

The process by which cancer cells spread to other parts of the body.

Medicine Year 1 Semester 1 (37 decks)

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