Shared Flashcard Set

Details

BMS 6001 - Test 2: Part 2
Cell junctions, motility, and ECM
35
Medical
Graduate
08/29/2010

Additional Medical Flashcards

 


 

Cards

Term
Occluding junctions
Definition

- tight junctions

- seal epithelial cells at apical layer

- separate apical proteins from basal layer

- composed of integral proteins (claudins and occludins) that form strands (more strands = more strength)

- Ca2+ dependent

Term
Anchoring junctions
Definition

- mediate cell-cell and cell-ECM attachment

- Four types:

  1. adherens
  2. desmosome
  3. hemidesmosome
  4. focal adhesions
Term
Zonula adherens (adherens junction)
Definition

Anchoring junction at apical layer that uses actin-mediated cell-cell attachment

- composed of cadherins (Ca2+ dependent glycoproteins)

- bind intracellular proteins (catenins, vinculin, α-actinin)

- can coordinate morphological tissue changes, e.g. forming a vessel

Term
Desmosome
Definition

Anchoring junction at the basolateral surface that mediates cell-cell attachement through intermediate filaments.

 

- gives mechanical strength

- composed of Ca2+ dependent cadherins (desmogleins, desmocollins)

- bind intracellular attachment proteins (desmoplakin, plakoglobin)

Term
Hemidesmosome
Definition

Anchoring junction that mediates cell-ECM attachment via intermediate filaments at the basal layer.

 

- binds extracellular laminin

- uses intracellular attachment protein, plectin

Term
Focal adhesions
Definition

Anchoring junction that mediates cell-ECM attachment via actin "stress fibers".

 

- important in movement

- bind extracellular fibronectin and laminin

- use intracellular attachment proteins (vinculin, talin, α-actinin)

 

Term
Gap junctions
Definition

- Mediate cell-cell communication

- located at basolateral surface, below adherens

- form connexon channel that allows small molecular transport

  • 6 connexins per connexon
  • aggregate in response to 2nd messenger stimuli
  • 14 different in the body
Term
Cell adhesion molecule (CAM)
Definition

Three main domains:

  1. ECM-domain that binds ECM or another CAM
  2. transmembrane domain
  3. cytosolic domain that binds adapter proteins

Types include cadherins, selectins, and integrins

Term
Types of cadherins
Definition
  • E-cadherin: epithelial
  • P-cadherin: placental or epidermal
  • N-cadherin: nervous or muscle

All are:

- Ca2+ dependent

- important in embryonic cell-adhesion

- exhibit homophilic binding.

Term
Selectin
Definition

Transmembrane, Ca2+ dependent cell-cell adhesion molecule

 

  • bind carbohydrates (lectins), i.e. heterophilic
  • found mostly in blood vessels
  • Three types:
  1. L-selectin: leukocytes (WBCs)
  2. P-selectin: platelets
  3. E-selectin: endothelial
Term
N-cell adhesion molecule (N-CAM)
Definition

Neural cell adhesion molecule:

  • NOT dependent on Ca2+
  • homophilic
  • 20 different types
  • specificity
Term
Extracellular matrix (ECM) structure and function
Definition

Composed of:

  • glycosaminoglycans (GAGs)
  • fibrous proteins (collagen, elastin, laminin, fibronectin)

Functions to:

  • Anchor cells
  • Mediate wound healing
  • Aid embryonic development

The ECM is created (fibroblasts) and mediated by the cells within it

Term
Glycosaminoglycan (GAG)
Definition

ECM component that is:

  • unbranched polysaccharide chain
  • forms gel (attracts Na+ and water) 
  • resists compression
  • synthesized in three steps:
  1. core protein in secretory pathway
  2. polysacch. addition in ER via glycosyl transferase
  3. saccharide elongation in Golgi
  • Two main types:
  1. Proteoglycan
  2. Hyaluron
Term
Hyaluron
Definition

Type of GAG that is:

  • (-) charged
  • forms gels and separates cells
  • crucial in heart development
  • crucial in wound healing
Term
Proteoglycan
Definition

Type of GAG that is composed of:

  • highly variable core protein (aggrecan, syndecan)
  • multiple GAGs

Function:

  • Sequester growth factors
  • present hormones to cell receptors
  • fill space and provide support
Term

Types of collagen

 

Definition

Type I: most abundant; skin and bone

Type II: cartilage

Type III: skin, blood vessels, organs

Type IV: forms basil network, gives tensile strength

 

Type IX & XII: promote further aggregation into fibers

Term

Collagen assembly

Definition
  1. Synthesis and glycosylation of procollagen in rough ER, formation of triple helix
  2. Further glycosylation and vesicle budding from Golgi
  3. Exocytosis
  4. Cleavage into collagen and self-assembly into fibrils in ECM
  5. Collagen fiber formation mediated by IX and VII in ECM

 

Term
Elastic fibers
Definition

ECM component that is:

 

  1. most prominent in skin, lungs, blood vessels
  2. composed of fibrillin and elastin
  3. synthesized only by fetal and juvenile fibroblasts
  4. excellent recoil and stretch
Term
Adhesive glycoprotein
Definition

Component of ECM that:

 

  1. binds other ECM components
  2. two types: fibronectin and laminin
Term
Fibronectin
Definition

Adhesive glycoprotein that:

 

  1. forms heterodimers
  2. plasma form associated with clotting & wound healing
  3. tissue forms fibrils
  4. R - G - D sequence mediates binding
Term
Laminin
Definition

Adhesive glycoprotein that:

 

  1. tends to form sheets
  2. binds epithelial cells to basement membrane

i.e. "laminins present on the lamina"

 

   3. associated with muscular and PNS regeneration

Term
Basal lamina
Definition

"Basement membrane"

 

Extracellular component that:

 

  1. underlie all epithelia and some other tissues
  2. thin sheet of proteins and carbohydrates
  3. provides basis for tissue repair, polarity, differentiation
  4. structure is tissue dependent:
  • epithelial basil lamina regulates transport
  • muscular basil lamina provides surrounding support
  • kidney basil lamina separates blood and urine
    • damage to lamina can lead to excretion of good proteins in the urine (Diabetes)
Term
Matrix metalloprotease (MMP)
Definition

ECM degradation peptide that:

 

  1. use calcium or zinc
  2. degrade ECM for differentiaion, proliferation, remodeling, and tissue repair
  3. usually up-regulated by metastatic cancer cells
Term
Serine protease
Definition

ECM degradation peptide that:

 

  1. regulated by serpins (serine protease inhibitor)
  2. regulated by cell-surface receptors
Term
Integrin
Definition

Cell-surface, integral membrane receptor associated with ECM binding:

 

  1. Beta1 - bind to ECM
  2. Beta2 - bind to other cells (only in lymphocytes)
Term
Microfilaments
Definition

Cytoskeletal component:

 

  1. gives strength and shape
  2. cell movement
  3. composed of actin filaments
    • polarity => grows from (+) end
  4. Muscle contraction
    • myosin motor protein


Term
Intermediate filaments
Definition

Cytoskeletal component:

 

  1. provide strength
  2. NOT polarized
  3. do NOT require ATP/GTP hydrolysis
Term
Microtubules
Definition

Cytoskeletal component:

 

  1. polymer of α & β dimers
  2. nucleate at centrosome (center of cell)
  3. polarized => grow at (+) end
  4. cilia & flagella use 9:2 arrangement
    • movement uses ATP
    • motor proteins, dyenin (-) and kinesin (+)
  5. can rapidly disassemble and reassemble
    • important for cell division
    • disrupted by taxol and cholchicine
Term
Cell Migration
Definition

Step-by-step extension of cell membrane for movement in tissue repair:

  1. Extension - using lamellipodium
  2. Adhesion - forms focal adhesion from stress fibers
  3. Translocation - cell body actually moves
  4. De-adhesion - breaks adhesions via stress fiber contraction

Actin and myosin polymerizing "stress fibers" drive movement

Term
Lamellipodium
Definition
Cytoskeletal actin projection on the mobile end of a migrating cell
Term
Filopodia
Definition
Slender spiky protrusion on slow moving migrating cells
Term
Membrane ruffle
Definition
Membrane protrusion that did not form focal adhesion, thus flips upwards
Term
Invadopodia
Definition

Invasive actin-based cellular protrusion:

  1. found on metastatic cancer cells
  2. contain adhesion proteins and matrix-degrading enzymes
Term
Kinesin
Definition

Motor protein associated with microtubules. Functions in cargo transport by utilizing ATP. Forms of kinesin vary and are cargo-specific.

 

Travels from (-) to (+) end.

 

Thus, travels from centrosome to cell membrane.

Term
Dyenin
Definition

Motor protein associated with microtubules. Associated with ATP-hydrolyzed cell movement

 

Moves from (+) to (-) end.

 

Thus, moves from PM to centrosome.

Supporting users have an ad free experience!