Tissue Architecture Flashcards
Why are cytoskeletons dynamic and adaptable?
Can disassemble, diffuse, and reassemble elsewhere
What forms of cytoskeleton filaments are thermally stable?
Multiple protofilaments
Single protofilament are not thermally stable
What filaments are resistant to stretching forces?
Intermediate filaments
What are the main components of cytoskeletal filaments?
Intermediate filaments
Microtubules
Microfilaments
Associated proteins
Mesh-like structure made up of intermediate filaments.
Nuclear lamina
Fuctions of intermediate filaments
Form a network throughout the cytoplasm and surround the nucleus
Rope-like properties give high tensile strength
Often further stabilized by accessory proteins
– Cross-link filaments into bundles
– Link to microtubules, actin filaments, and cell-junctions
What intermediate filament is found in epithelial cells?
Keratin filaments
What intermediate filament is found in connective tissue cells, muscle cells, and glial cells?
Vimentin and vimentin-related filaments
What intermediate filament is found in nerve cells?
Neurofilaments
What is the nuclear intermediate filament?
Nuclear lamins
Functions of microtubules
Provide tracks for transport vesicles
Mitotic Spindle formation
Cilia and Flagella
Binds and stabilizes microtubules
taxol
Binds tubulin dimers and prevents polymerization.
Colchicine, colcemid, vinblastine, vincristine
What is F actin composed of?
Twisted polymer of G-actin (globular) that has structural polarity
Many must be in association with other proteins to be stable
Binds and stabilizes actin filaments
Phalliodin
Caps actin filament plus end, preventing polymerization there
Cytochaslin
Binds actin monomoers and prevents polymerization
Latrunculin
How can actin filaments be modified when bonded to other proteins?
Stabilize
Strengthened
Cross-linked
Organizes
What are some extracellular proteins?
Perlecan
Sheet formin collagen (IV)
Fibrillar collagen (I,II,III)
Lamninin
Fibronectin
Nidogen/entactin
Main structural protein in ECM/connective tissue and basal laminae.
Collagen
How do collagen types differ?
28 types
Homotrimers
Heterotrimers
Form collagenous triple helix
Can be fibers, sheets, or transmembrane structures
Where is the precollagen prepared for secretion
Secretory Vesicles
Scurvy is caused by loss of what cofactors
Ascorbate or Iron
Disease caused by defects in collagen or enzymes contributing to synthesis.
Ehlers-Danlos Syndrom
Weakens connective tissue in the skin, bones, blood vessels, and organs
Links cells to extracellular matrix, or basil lamina
Focal Contacts
What are the four classes of Cell Adhesion Molecules
Cadherins (e-cadherins)
Ig-superfamily CAMs (NCAM)
Integrins (avB3)
Selectins (P-selectins
What are the common aspects of cadherins?
Ca2+ dependent adhesion molecule – Important in formation of junctions between cells (epithelial “sheets”) such as desmosomes and adherens junctions
– Homophilic interactions (extracelluar)
– Interact with cytoskeleton (actin)
What are classic cadherins?
Cytoplasmic domain interacts with beta-catenin, alpha-catenin, and p120
Linked to the actin cytoskeleton
Associated with adherens junctions
What are the classic cadherin examples listed?
E-cadherin (epitheilial)
VE-cadherin- (vascular-endothial)
N-cadherin- (neural)
What are atypical cadherins?
Function without interaction with catenins or a link to the actin cytoskeleton.
Example of an atypical cadherin.
LI-cadherin - liver-intestine cadherin
How can Cadherin serve in the detection of metastatic tumors?
Epithelial to mesenchymal transition (EMT)
In bladder cancer, a decreased E-cadherin and increased N-cadherin can mark metastasis.
Family of more than 25 Calcium-independent transmembrane glycoproteins that are involved in immune cell interactions.
Ig Superfamily CAMS
What type of bonding does the Ig Superfamily participate in?
What is the function of this binding?
Homophilic and heterophilic binding
Involved in recognition, binding, or adhesion processes of cells
Contain a variable number of immunoglobulin-like domains.
Expressed on vascular endothelial cells and bind to various integrin molecules.
ICAM, VCAM-1, PECAM-1, NCAM
the NP does IV
Contain Ig-like and mucin-like domains
Expressed on mucosal endothelium to direct lymphocyte entry into mucosa.
MAdCAM-1
What are selectins and what are their roles?
Family of calcium-dependent glycoproteins
Bind to extracellular carbohydrates
Play important roles in host defense mechanism
How do selectins play a role in the host defense mechanism?
Increased presentation during local inflammatory response
WBC surface markers include carbohydrates which act as ligands for selectins
Low-affinity of selectins to ligands allows for leukocyte “rolling” during leukocyte adhesion cascade
What are the types of selectins?
Endothelial (E)-selectin
Leukocyte (L)-selectin
Platelet (P)-selectin
How many integrins are there?
15 α and 8β subunits form over 20 heterodimeric integrins
Functions of integrins
Couple the extracellular matrix to cell cytoskeleton
Can activate signaling pathways
Cell-Cell interactions via β2 family
How do integrins activate signaling pathways
Interactions with receptor tyrosine kinase
Take part in regulating growth, division, survival, differentiation, apoptosis
B2 Integrins are important for cell-to-cell interactions for what?
On leukocytes they allow for adhesion and transmigration to sites of infection.
What important molecule is synthesized in the RER for collagen production?
RER = Synthesis of precollagen
Where does hydroxylation of proline and lysine, glycosylation of select hydroxylysine residues of precollagen occur?
The Endoplasmic Reticulum
Where does self-assembly of the trimeric molecule of precollagen occur?
Golgi Apparatus and ER
How does self-assembly of the trimeric molecule of collagen occur?
With sulfide bonds initiating it in the c-terminus.
Where is precollagen cleaved to collagen?
In the extracellular environment
Describe the movement of microfilaments.
Faster movement on the postive end. dissociation or slower growing of the negative end
What role does gamma tubulin play in microtubules?
Nucleation of the minus end provides area from which microtubules can grown
What three chains make up collagen?
3 alpha chains total
2 alpha1
1 alpha2
Vitamin C is a cofactor of what?
Prolyl hydroxylase, which hydroxylates collegen
4 cell connections and junctions
Anchoring
Occlluding - maintain cell polarity
Channel-forming
Signal-relaying
4 types of Anchoring junctions
Adherens junctions
Desmosomes
Hemidesmosomes
Focal, fibrillar, and Ad adhesions
