Tissue Architecture Flashcards
What are some characteristics of microfilaments?
Composed of actin (F-actin) filaments
Present in all cell types
Generally unstable
What is the function of microfilaments?
Essential for cell movement (locomotion, phagocytosis, cell division, contraction, etc)
Many proteins can bind to and modify actin properties. These proteins can do what?
Stabilize, strengthen, cross link and organize
What is the function of microtubules?
Crucial organizational role in all eukaryotic cells
Involved in cell division
What are some characteristics of microtubules?
Long stiff hollow tubes
Can undergo rapid assembly and disassembly
Describe some characteristics of intermediate filaments
Rope like properties that give high tensile strength
Can be cytoplasmic or nuclear
Often further stabilized by accessory proteins
Form mesh like structure called nuclear lamina
How do accessory proteins further stabilize intermediate filaments?
Cross link filaments into bundles
Then link to microtubules, actin filaments and cell junctions
What is the role of the nuclear lamina created by intermediate filaments?
Play a role in strengthening and stabilizing the nuclear envelope
Clinical importance: Hutchinson-Gifford Progeria syndrome (HGPS) which causes individuals to undergo accelerated aging - caused by a mutation in the nuclear lamina leading to nuclear instability
Characteristics of the ECM and basal lamina
Components produced intracellularly and can be secreted or can aggregate
ECM interacts with cells/tissues via cell adhesion proteins
Composition and properties controlled and vary by tissue type, location, etc
List examples of cytoplasmic intermediate filaments
Keratin filaments in epithelial cells
Vimentin and vimentin-related filaments in CT cells, muscle cells and glial cells
Neurofilaments in nerve cells
What is the main example of a nuclear intermediate filament?
Nuclear lamina in all animal cells
What are the extracellular matrix proteins?
Proteoglycans (perlecan), collagens and multi adhesive matrix proteins (laminin, fibronectin and nidogen/entactin)
What is collagen?
Main structural protein in ECM/CT and basal lamina
Composed of trimeric proteins
Associate as fibers, sheets or transmembrane structures
Affected by nutrient deficiencies and genetic conditions
Summarize the steps in the synthesis and processing of collagen
Takes place in the rough ER
- Pre-collagen is formed
- Hydroxylation of residues allows for trimeric molecules to form and remain stable
- Assembly into procollagen
- Processed by the Golgi (post translational modification)
- Secreted in ECM
- Enzymatically cleaved
- Collagen molecules self assemble
What is a defect that is associated with collagen?
Scurvy (loss of cofactor like ascorbate or iron)
Defect in hydroxylation process
Results in decreased wound healing, loss of teeth, anemia, pale skin and sunken eyes
What are the four main types of cell connections and junctions?
Anchoring junctions, occluding junctions, channel forming junctions and signaling relaying junctions
What are anchoring junctions?
Adherens junctions, desmosomes, hemidesmosomes
Link cells together and strengthens contacts between cells and the ECM
What are occluding junctions?
Tight junctions
Seal gaps between cells through cell-cell contact making an impermeable barrier for diffusion
What are channel forming junctions?
Gap junctions
Link cytoplasm of adjacent cells allowing transport of molecules to occur between cells
What is an example of signal relaying junctions?
Synapses
What are the four major families fo cell adhesion molecules (CAMs)
Cadherins
Integrins
Selectins
Ig-superfamily
Describe the cadherin superfamily
Ca dependent cell-cell CAMs
Important in formatting of junctions between cells (epithelial sheets)
Desmosomes and adherens junctions
Ex. E, N, VE and LI cadherins
What are E cadherins?
Epithelial cadherin
What are N cadherins?
Neural cadherin
What are VE cadherins?
Vascular endothelial cadherin
What are LI cadherin?
Liver-intestine cadherin
Describe integrins
Composed of 15 alpha and 8 beta subunits which form over 20 heterodimeric integrins
Couple the ECM to cell cytoskeleton
Can activate signaling pathways
Describe the cell-cell interactions integrins have via the beta2 family
Integrins on leukocytes allow for adhesion and transmigration to site of infections
Describe selectins
Family of Ca dependent glycoproteins
Bind to extracellular carbohydrates/ligands
Include E-selectin, L-selectin and P-selectin
What role do selectins play in host defense?
Increased presentation during local inflammatory response
WBC surface markers include carbohydrates and integrins (beta-2) which acts as ligands for selectins
What are E-selectins?
Endothelial selectins
What are L-selectins?
Leukocyte selectins
What are P selectins?
Platelet selectins
What are some characteristics of the Ig superfamily of CAMs?
Family of more than 25 Ca independent transmembrane glycoproteins
Homophilic and heterophilic binding
Involved in recognition, binding and adhesion processes of cells as well as immune cell interactions
Describe the immune cell interactions of ICAM, VCAM-1, PECAM-1 and NCAM of the Ig superfamily
Contain a variable number of immunoglobulin like domains
Expressed on vascular endothelial cells and bind to various integrin molecules
Describe the immune cell interactions of MADCAM-1 in the Ig superfamily
Contain immunoglobulin like and mucin like domains
Expressed on mucosal endothelium to direct lymphocyte entry into mucosal tissue
What is phalloidin?
An actin specific drug that binds to and stabilizes the actin filaments
Found in mushroom caps
Derivatives are used in microscopy by aiding in visualization of cell shape
What is taxol?
A microtubule specific drug
Used to bind and stabilize microtubule filaments
Used in cancer tx (prevents cell division in cancer cells but can also have an affect on normal cells undergoing cell division)
What are colchicine/colcemid and vinblastine/vincristine?
Microtubule specific drugs that bind tubulin dimers and prevent their polymerization
Used in cancer tx (prevents cell division in cancer cells but can also have an affect on normal cells undergoing cell division)
