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Histology Exam 1 > Lec5 > Flashcards

Lec5 Flashcards

1
Q

Characteristics of Basement Membrane

A
  • Separates epithelial layer from its connective tissue support
  • 50-80nm thick
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2
Q

the 2 components of basement membrane

A
  1. Basal Lamina produced by epithelium

2. reticular lamina, prodiced by connective tissue

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3
Q

Basal lamina contains:

A

laminin, fibronectin, type 4 collogen, heparin sulfate proteoglucans, nidogen (entactin). Components are glyco proteins which are PAS positive

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4
Q

Reticular Lamina Contains:

A

type 3 collogen (reticular fibers) Components are glyco proteins which are PAS positive

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5
Q

Laminin

A
  • Maj component of basal lamina; it consists of three chains, A, B, gamma
  • has binding sites for integrins, type 4 collagen, entactin and proteoglycans (ie heparin sulfate)
  • ties everything together in BL
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6
Q

Fibronectin

A
  • a protein made up of of 2 pp chains cross-linked by disulfide bonds
  • 2 forms: cellular (produced by fibroblasts) & plasma (secreted into bloodstream by hepatocytes)
  • binding sites for heparin (proteoglycan), integrins, collagen, fibrin
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7
Q

4 CAMs, 2 Ca Dep/ 2 Ca Independent

A
  1. Cadherins 2. Selectins 3. Integrins 4. Ig Superfam
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8
Q

Classical Cadherins

A
  • major Components in Ca-mediated adherens junctions
  • typically cis and trans homophilic dimers
  • include: e-cadherins found in epithelial, N-nerve, P-placenta
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9
Q

E-Cadherins

A

-most common type, form dimers via a
HVA binding face (histidine, valine, alanine) found at tip of extracellular end of cadherin molecule, Ca ions bind to 4 extracellular domains and facilitate cis-homophillic dimers

-loss of e-cads associated w invasive behavior brain tumors

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10
Q

Catenins

A

-small proteins that link the cytoplasmic end of a cadherin with cytoplasmic actin, serve as maj. interafce between cads that hold adjacent cells together and the actin cytoskeletons of those cells
-3 forms:
B and Gamma-attached to cytoplasmic end of cadherin, beta ttached to alpha
alpha: binds directly to cytoplasmic actin

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11
Q

Selectins

A

binds to carbohydrates so part of lectin group
-4 carb binding iste located at carb-recog. domain (CRD) at extracellular end of selectin
-Ca binding sites also found near CRD and Ca is reqd for binding activity
-involved in extravasation and homing (17)
p-platelets, e-endothelial, L-leukocytes

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12
Q

Integrins

A

Glycoproteins mainly involved in cell-extracellular matrix interactions

  • consist of 2 subunits: 1 alpha (s-s) (17 kinds) and 1 beta (8 kinds)
  • extra cellular domains bind to molecules in extracellular matrix such as fibronectin and laminin
  • in hemidesmosomes integrins link basal domains of cells to ECM via intracellular tonofilamnets
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13
Q

Ig Superfam

A

-possess an extracellular segment w 1 or more folded domains characteristic of immunoglobulins
-members: N-CAM = cell adhesion molecules are neural adhesion molecules that mediate both homo and hertrophilic interactions
I-CAM1 & I-CAM2- 1 facilitates transendothelial migration of leukocytes

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14
Q

Adherins

A

A category of junctional complexes, anchor cells together and reinforce the physical integrity of tissues and cells that make up th tissues
-found on basolateralsurfaces of epithelial cells

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15
Q

Occludens

A

A category of junctional complexes, establish an impermeable barrier btwn adjacent cells, esp. epithelial, preventing paracellular transport & maintains conc. differnces btwn environemnts on either side of epithelial sheets

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16
Q

Gap Juntions 1

A

A category of junctional complexes, composed of molecular pores that enable cells to rapidly exchange ions and small molecules tht help coordinate activities among the cells that make up the tissue

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17
Q

Zonula

A

A type of junction that can be either adherens or occludens, zonula complexes travel all the way around the cell & link all neighboring cells to central cell. “belt like complexes”
-associated w intracellular actin

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18
Q

Macula

A

a “spot” or snap-like junction. Adherens variety and often referred to as desmosomes (lateral domain) or hemidesosome (basal domain), associated w intracellular intermediate filaments (tonofilaments)

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19
Q

Hemidesmosome

A

anchroing junctions that anchor the basal domain of the epithelial cell to basal lamina

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20
Q

Hemidesmosome consists of:

A

cytoplasmic plate associated w int. filamnets such as keratin, a membrane plaque linking the hemidesmosome to the basal lamina via anchrng filaments (laminin 5) and integrin
-at 1 time hemidesmosome were thoght to be half a desmosome

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21
Q

Zonula Occludens

A

-“tight junctions”, belt like occluding junction, barrier against paracellular transport

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22
Q

JAMs and Nectin

A

members if Ig Superfam, stabalized by s-s bonds, form cis homodimers that facilitate cell adhesion
-nectin is associated w intracelular molecule afadin, JAMs w afadin & ZO-1

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23
Q

Focal Adhesions

A

spots that anchor the cell to the ECM via integrins, may be very stable or high turnover, ECM portion of the integrins may be folded close to the plasma membrane and unattached to ecm, cystolic signals may cause the integrin heads to unfold and attach to ECM components such as fibronectin or laminin

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24
Q

Gap Junctions 2

A

communicating junction btwn cells, composed of connexons each consisting of 6 connexins, forming a hexagonal structure w hallow center, connexons often clustered in patches, move molecules up to 1.2 nm in diamter

  • chemical or electrical coupling
  • related pathologies are charcot marie tooth, congenital cataracts
25
Q

3 protein structures that make cytoskeleton

A

microfilaments (actin) (7 nm thick)
intermediate filaments (8-10nm thick)
Microtubules (25 nm)

26
Q

Actin Microfilaments

A

Highly conserved, 7nm, filaments up to 7 microm, filamnets org. into bundles and 3D networks, bind to specific transmembrane proteins either directly or indirectly, exist as G-actin or F-actin, 3 varities A-actin in muscle, b and gamma in non muscle

27
Q

first step in actin polymerization is:

A

nucleation, a trimer is formed, add’ll actin monomers can then be added to either end

28
Q

actin assembly

A

each monomer has ATP binding site, must be atp to add to f-actin, rate of growth proportional to cytosolic conc of actin monomers, ADP-actin disassocites mre readily, barbed end grows 5-10 times faster than pointed end

29
Q

treadmilling

A

intermediate conc of actin in cytosol favor a dynamic equilibrium btwn minus end and plus end

30
Q

Higher conc of G-actin favors:

A

net addition of growing F-actin at both ends, remember barbed end grows faster, and therefore growth of filament

31
Q

Cytochalasins

A

Drug that affects actin polymerization; bind to barbed ends, block elongation, can inhibit movement (ie cell division)

32
Q

Phalloidin

A

Drug that affects actin polymerization; binds to actin filaments and prevents dissociation, can be labeled w fluorescent dyes to allow visualization of actin filaments

33
Q

Spectrin

A

An Actin-Binding protein found in RBCs, binds cortical cytoskeleton to the plasma membrane

34
Q

Dystrophin

A

An Actin-Binding protein that binds cortical cytoskeleton to the plasma membrane

35
Q

Villin and Fimbrin

A

An Actin-Binding protein that cross-links in micro villi

36
Q

Calmodulin & Myosin 1

A

An Actin-Binding protein that cross-links actin to plasma membrane in microvilli

37
Q

à-Actinin

A

An Actin-Binding protein that cross links stress fibers and connects actin to protein-plasma membrane complexes

38
Q

Filamin

A

cross-links actin at wide angles to form screen-like ges

39
Q

Tymosin

A

An actin binding molecule controlling treadmiling that captures actin monomors; prevents monomors from being polymerized

40
Q

Profilin

A

An actin binding molecule controlling treadmiling that binds to actin monomors and prevents monomors from being polymerized, facilitates exchange of bound ADP for ATP-which favors polymerization

41
Q

Type of TP needed to assemble actin

A

only ATP-actin monomers can be assembled into F-actin whether on barbed (faster) or pointed end

42
Q

Gelsolin

A

An actin binding molecule controlling treadmiling that destabalizes F-actin and caps actin filaments, preventing loss and addition of g-actin, in presence of Ca ion, fragments actin filament and remains bound to + end

43
Q

Cofilin

A

An actin binding molecule controlling treadmiling that triggers depolymerization of ADP-bound actin at the - end

44
Q

Arp2/3

A

An actin binding molecule controlling treadmiling that initiates growth of f-actin from sides of exisiting filament-casues branching

45
Q

Phalloidin

A

An actin binding molecule controlling treadmiling that prevents depolymerization by binding to actin filaments

46
Q

Latrunculins

A

An actin binding molecule controlling treadmiling that binds to g-actin and induces f-actin depolymerization

47
Q

Intermediate Filaments

A

are 8-10nm thick, tensile strength in cells like neurons and muscles cells, strenghthen epithelial cells as desmosomes/hemi, all have common monomer, head and tail domains determine specific functions

48
Q

Intermediate filaments functions

A

form a cytoplasmic network in most cells, associate with other cytoskeletal elements to form a scaffolding that organizes the internal structure of the cell

49
Q

int. medite filament assembly

A

central rod of 2 polypeptides form a coiled dimer (rods are aligned tail 2 tail and head 2 head)

  • dimers associate in a staggered antiparallel fashion to form tetramers-bc of antiparallel association of dimers, polymerized filaments dont have distinct ends there4 more stable than actin and no dynamics like tradmilling
  • tetramers assemble end to end to form protofilaments and 8 protofilaments wound together to form filaments
50
Q

Intermediate Filament Type I

A

Acidic Keratins

51
Q

Intermediate Filament Type II

A

Neutural to basic keratins

52
Q

Intermediate Filament Type III

A

vimentin

  • desmin
  • glial fibrillary
  • peripherin
53
Q

Intermediate Filament Type IV

A

neurofilaments

54
Q

Intermediate Filament Type V

A

nuclear lamins

55
Q

Intermediate Filament Type VI

A

nestin

56
Q

Microtubule Characteristics

A

25 NM, composed of tubulin dimers (alpha and beta unit)

57
Q

Microtubule Plus end

A

Grows more rapidly than minus end in presence of low Ca ion conc.

58
Q

Factors that inhibit microtubule polymerization

A

Colchicines, Colcemid, Vincristine, Vinblastine

59
Q

Factors that stabalize microtubules

A

Taxol

Histology Exam 1 (3 decks)

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