MFM Week 2 Cell adhesion and membrane Junctions
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Created by:
costa_alimonos on August 7, 2012
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Week 2
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55 terms
Terms | Definitions |
|---|---|
 Name the components of ECM | Fibrous proteins - Fibronectin, collagen, elastic fibers, laminin Proteoglycans |
| Where are ECM components made, and where are they assembled into higher order? | Inside the cell, outside the cell |
| What is ECMs role in connective tissue? | Carries the mechanical load |
| What carries the load for epithelia cells? | The cells themselves - no help from ECM |
| What is fibronectin? | Glycoprotein consisting of 2 monomers (dimer) linked by disulfide bond. |
| What secretes fibronectin? | Fibroblasts |
| What is one important role fibronectin plays? | Wound healing |
| Where is collage protein found? | Bone, tendon, skin |
| What percentage of body mass does collage constitute? | 25% |
| What makes up a collagen super helix? | 3 polypeptides |
| What do super helices assemble into? | Collagen fibrils |
| What do collage fibrils form? | Collagen Fibers |
| Cells that produce collagen | Fibroblasts (skin, tendon) and osteoblasts (bone) |
| What is the precursor form of collagen? | Procollagen |
| What cleaves procollagen and where? | Proteinases, outside the cell |
| What causes hyperextensible skin? | Genetic defect in procollagen proteinase |
| Where is elastic fibers found? | Smooth muscle, blood vessels, skin |
| What two proteins make up elastic fibers? | Elastin, fibrillin |
| Describe the structure of an elastic fiber | Loose, unstructured, polypeptides covalently cross linked into rubber like meshwork |
| What is the major protein found in basal lamina | Laminin |
| What are the trimeric proteins that compose laminin | alpha, beta, and gamma subunits |
| What role does laminin play in ECM and how | Provide support by binding to collagen and integrins |
| What is a proteoglycan comprised of? | Polysaccharides (glycosaminoglycans aka GAG) linked to a core protein |
| What are the 3 main groups of GAGs | Hyaluronic acid, Chondroitin sulfate, keratin sulfate |
| Where are proteoglycans found? | Interstitial connective tissue - i.e. synovial fluid, vitreous fluid, cartilage |
| What are the 4 superfamilies of cell adhesion molecules (CAM) and are they Ca dependent? | Ca independent - Immunoglobulin-like = I-CAMs Ca dependent - Cadherins, Integrins, Selectins |
| Name 3 examples of I CAM and where they can be located | N-Cams - Neural CAM VCAM-1 - Vascular CAM PECAM-1 - Platelet endothelial CAM |
| Name three types of Cadherin and where they can be located | E Cadherin - Epithelial Cells N-Cadherin - Neural Cells P-Cadherin - Placenta and epidermis |
| What cell junction molecules can you find cadherins in? | Adherns, Desmosomes |
| Integrins are transmembrane heterodimers. Where do they bind to extracellularly? Intracellulary? | Fibronectin, actin filaments via adaptor proteins |
| Where is stress transmitted to when there is tension between the cell and matrix in integrins? | Cytoskeleton |
| What is a result when integrin dimers on one side of the membrane are activated? | Results in the activation of integrins on the other side of the membrane |
| What binding sites does fibronectin contain? | Binds to collagen and integrin |
| What does the fibronectin-integrin complex provide? | A bridge between extracellular matrix and actin cytoskeleton of cell |
| Name the three subsets of selectins | E-Selectin - Found in endothelial cells and induced by inflammation L-Selectin - Leukocytes P-Selectin - Platelets and endothelial cells |
| To what and where do selectins bind? | To glycans on surfance of other cells |
| What is extravasation? | Movement of leokocyte from circulation to site of tissue damage/infection |
| What are the steps in extravasation? | Chemo-attraction, rolling adhesion, tight adhesion, transmigration |
| Describe Chemo-attraction | Macrophages in affected tissue release cytokines to attract leukocytes |
| Rolling adhesion | Carbs on leukocyte plasma membrane bind to selectins on plasma membrane of endotheial cells lining the inner wall of blood vessel |
| Tight Adhesion | Integrins on leukocytes bind to I-CAMs on endothelial cell surfaces with high affinity and immobolize leukocyte |
| Transmigration | Leukocyte passage through gaps between endothelial cells is mediated by PECAMs |
| What are the five families of membrane junctions? | Tight, adherens, desmosomes, gap, and hemidesmosomes |
| What proteins form tight junctions? | Claudins and occulins |
| Functions of tight junctions | Hold cell together, prevent passage of molecules/ions, and maintain polarity by forming ribbon around entire cell |
| Adherins junctions are composed of what protein? How do they bind? | Cadherin - Bind to other cadherins of neighboring cells, which connect to the intracellular actin cytoskeleton |
| Adherins purpose? | Join adjacent cells by forming ribbon around entire cell |
| What is the role of desmosomes and what do they bind? | Resist shear forces, Keratin filaments |
| The cytoplasmic plaque of desmosomes is composed of: | Plakoglobin, desmoplakin |
| What cadherin family proteins link adjacent desmosomes? | Desmoglein, desmocollin |
| What is the role of gap junctions | Provide channel between two adjacent cells to allow small H2O molecules/ions to pass |
| What complexes form gap junctions? | Connexons (composed of 6 subunits) |
| Where are gap junctions found? | Heart muscle - allow electrical coupling |
| What is the role of hemidesmosomes? | Attach cells to extracellular matrix by connecting the basal surface to the basal lamina |
| What filaments are hemidesmosomes associated with? | keratin filaments |
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