Tissue Architecture

Question 1

What are the functions of the cytoskeleton on the subcellular, cellular, and tissue level?

Answer 1

• subcellular: organization, tensile strength, chromosome segregation, cell polarity, vesicular movement
• cellular: cell morphology/shape, motility, cell adhesion, division
• tissue: muscle contraction

Question 2

• type of filament
• actin filaments (F-actin)
• present in all cell types
• generally unstable
• essential for cell movements: locomotion, phagocytosis, cell division, contraction, etc.

Answer 2

microfilaments

Question 3

What are modifications to actin proteins by other bound proteins?

Answer 3

• stabilization
• strengthen
• cross-linking
• organizing

Question 4

What are drugs that affect actin filaments, what affect do they have?

Answer 4

• phalloidin: binds and stabilizes filaments (death cap mushroom, used in microscopy)
• cytochalasin: caps filament plus ends, prevents polymerization there
• latrunculin: binds actin monomers and prevents their polymerization

Question 5

• type of cytoskeleton filament
• crucial role in organization in all eukaryotic cells
• long, stiff, hollow tubes
• can undergo rapid assembly and disassembly
• (+/-) sides like actin, dimers are added to (+) end
• push/pull cells a part during cell division
• shape, organize, and act are roads to move things around
• comprise flagella and cilia

Answer 5

microtubules

Question 6

What are drugs that affect microtubules and what is their action?

Answer 6

• taxol: binds and stabilizes microtubules
• colchicine, colcemid: binds tubulin and prevents their polymerization
• vinblastine, vincristine: binds tubulin dimers and prevents their polymerization

(some of these meds are occasionally used in cancer tx to prevent formation of microtubules to prevent cell division)

Question 7

• type of filament
• rope-like properties give these high tensile strength
• often further stabilized by accessory proteins: cross-link filaments into bundles, link to microtubules, actin filaments, and cell junctions
• form mesh-like structure called nuclear lamina
• gives strength/stability to cell/tissue

Answer 7

intermediate filaments

Question 8

Intermediate Filaments:

Answer 8

• keratin
• vimentin and vimentin-related filaments
• neurofilaments
• nuclear lamins

Question 9

• condition due to lack of nuclear lamins which causes cellular instability
• mutations in type A lamin
• sx: accelerated aging

Answer 9

Hutchinson-Gilford Progeria Syndrome (HGPS)

Question 10

• components are produced intracellularly and secreted/aggregate
• matrix that interacts w/ cells/tissues via adhesion proteins
• functions: anchor/engluf cells to define boundaries, cell polarity, cell survival/proliferation, cell movement
• composition and properties controlled/vary by tissue type, location of cell, etc.
• protein groups: proteoglycans, collagens, multi-adhesive matrix proteins

Answer 10

extracellular matrix and basal lamina

Question 11

• main structural protein in ECM/connective tissue and basal laminae
• composed of trimeric proteins
• associate as fibers, sheets, or transmembrane structures
• affected by nutrient deficiencies and genetic conditions

Answer 11

collagen

Question 12

How is collagen made/processed in the cell in terms of locations:

Rough ER:

Lumen of ER:

Lumen of ER and Golgi:

Secretory vesicle:

Extracellular:

Answer 12

Rough ER: synthesis of preprocollagen; insertion of procollagen molecule into lumen of ER

Lumen of ER: hydroxylation of proline and lysine residues; glycosylation of selected hydroxylysine residues

Lumen of ER and Golgi: self-assembly of the tropocollagen molecule, initiated by disulfide bond formation in th carboxy-terminal extensions; triple helix formation

Secretory vesicle: procollagen prepared for secretion from cell

Extracellular: cleavage of the propeptides, removing the amino and carboxy-terminal extensions, and self-assembly of the collagen molecules into fibrils and then fibers

TLDR: synthesized in the ER, processed in Golgi, further processed extracellularly

Question 13

What is the mechanism of action of vitamin C deficiency leading to scurvy?

Answer 13

• vitamin C deficiency leads to decreased hydroxylation of the proline/lysine residues comprising procollagen
• this leads to failure of the procollagen to form the triple helix, leading to tissue instability
• sx: decreased wound healing, loss of teeth, anemia, pale skin, sunken eyes

Question 14

What are the 4 types of cell connections/junctions?

Answer 14

• anchoring junctions
• occluding junctions
• channel-forming junctions
• signal-relaying junctions

Question 15

• type of cell junction
• link cells together and strengthens contact between cells and the ECM
• ex: adheren junctions, desmosomes, hemidesmosomes

Answer 15

anchoring junctions

Question 16

• type of cell junction
• seal gaps between cells through cell to cell contact, making an impermeable barrier for diffusion
• ex: tight junctions

Answer 16

occluding junctions

Question 17

• type of cell junction
• link cytoplasm of adjacent cells allowing transport of molecules to occur between cells
• ex: gap junctions

Answer 17

channel-forming junctions

Question 18

• type of cell junction
• ex: synapses in the nervous system

Answer 18

signal-relaying junctions

Question 19

What are the 4 major types of cell adhesion molecules (CAMs)?

Answer 19

• cadherins: cell-cell
• intergrins: cell-ECM or cell-cell
• selectins: cell-cell in circulatory system (leukocytes/endothelial)
• Ig superfamily: variable based on tissue

Question 20

• type of cell adhesion molecule group
• Ca2+ dependent adhesion
• important in formation of junctions between cells (epithelial sheets), for example, desmosomes and adherens junctions
• naming is based on location

Answer 20

cadherins

Question 21

• subgroup of cadherins
• type I (ex: E-cadherin, N-cadherin, R-cadherin): Ca2+ dependent homophilic adhesion function, cytoplasmic domains interact w/ beta-catenin, alpha-catenin, and p120
• type II (ex: VE-cadherin): linked to the actin cytoskeleton, a/w adherens junctions

Answer 21

class cadherins

Question 22

• subgroup of cadherins
• T-cadherin and LI-cadherin
• function as homophilic adhesion proteins w/o interaction w/ catenins or link to actin cytoskeleton

Answer 22

atypical cadherins

Question 23

• type of cell adhesion molecule group
• 15alpha and 8beta subunits form over 20 heterodimeric integrins
• couple the ECM (fibronectin, collagen lamin) to cell cytoskeleton (intracellular actin)
• cell-cell interactions via beta2 family (these molecules on leukocytes allow for adhesion and transmigration to sites of infection)
• can activate signaling pathways and initiate multiple cellular responses

Answer 23

integrins

Question 24

• type of cell adhesion molecule group
• calcium dependent glycoproteins
• bind to extracellular carbohydrates/ligands/integrins
• important role in host defense mechanism (increased presentation during immune response, WBC has carbs and integrins (beta2) on the surface which act as ligands for these molecules)
• ex: endothelial (E), leukocyte (L), and platelet (P)

Answer 24

selectins

Question 25

- type of cell adhesion molecule group - family of more than 25 calcium-independent transmembrane glycoproteins - functions: **immune cell interactions**; homophilic/heterophilic binding; **self recognition**, binding, or adhesion processes of cells; stable adherent junctions; can give a cell polarity - ICAM, VCAM-1, PECAM-1, NCAM: contain variable number of immunoglobulin-like domains, expressed on vascular endothelial cells and bind to various integrin molecules - MAdCAM-1: contain Ig-like and mucin-like domains, expressed on mucosal endothelium to direct lymphocyte entry into mucosa

Answer 25

Ig superfamily of CAMs