Exam 3 Theisen review PART 2 Flashcards
Effects of Rho GTPases on Actin Organization:
Rho
Rho activation promotes both the bundling of actin filaments with myosin II filaments into stress fibers and the clustering of integrins and associated proteins to form focal contacts (FEET).
Effects of Rho GTPases on Actin Organization:
Cdc42
activation triggers actin polymerization and bundling to form filopodia.
Effects of Rho GTPases on Actin Organization:
Rac
activation promotes actin polyerization at the cell periphery leading to the formation of Lamellipodia extensions.
Rac/Cdc42 =
Rho =
Rac/Cdc42= dynamic actin Rho= rigid actin.
Two main ways to connect animal cells and provide the strength:
-Connective tissue: such as bone or tendon, ECM is plentiful and cells are sparsely distributed within it.
Epithelial Tissue: The cytoskeleton of cells is linked from cell to cell by anchoring junctions and the ECM is scanty, consisting mainly of a thin mat called the BASAL LAMINA.
-CELL-matrix attachments bond epithelial tissue to the connective tissue beneath it.
Transmembrane adhesion proteins
- play a central role in anchoring junctions.
- spand the membrane with one end linking to cytoskeleton inside the cell and the other end linking to other structures outside the cell.
- Two families-based on external attachments
- —cadherin and Integrin
—Two other superfamilies fo cell-cell adhesion molecules are selecting and immunoglobulin (Ig) superfamily.
Transmembrane protein that mediates cell-cell connection
Cadherin
Transmembrane protein that mediates attachment of cells to matrix?
Integrin
Adherens Junctions
- are an essential part of the machinery for modeling the shape of multicellular structures
- primarily present in epithelia.
- often for a continuous adhesion belt (zonula adherens) close to apical face, encircling each of the interacting cells in the sheet.
- within each cell, a contractile bundle of acting filaments lies adjacent to the adhesion belt, oriented parallel to the plasma membrane and tethered to it by the cadherins and their associated intracellular anchor proteins.
The intermediate filament networks of adjacent cells are indirectly connected to one another through _____ and to the basal lamina through __________?
desmosomes, hemidesmosome
The particular type of intermediate filaments attached to the desmosomes depends on the cell type. What is in most epithelial cells?
keratin filaments.
Right junctions consist of a branching network of _______ ________ that completely encircles the apical end of each cell in the epithelial sheet.
Sealing Strands
The tight junctions is seen as a series of ______ ______ between the two interacting plasma membranes, each connection corresponding to a sealing strand.
Focal connections
What are the two main tight junction proteins?
Claudin (main) and occluding
How is the sealing strand of a tight junction composed?
a long row of 4 pass transmembrane adhesion proteins embedded in each of the two interacting plasma membranes.
To fully polarize, the epithelial cell must then separate the apical from basolateral surfaces via?
Right junction formation
What three conserved polarity protein complexes control polarization process and maintain polarity?
Par, Crumbs and Scribble.
Gap junctions are made up of 4 pass transmembrane proteins called
connexons (hexameric channels contain 6 protein subunits)
What proteins are contained in the basal lamina?
laminin and type IV collagen
An integrin molecule consists of two noncovalently associated subunits ___ and ____
alpha and beta
Both subunits of integrin span the cell membrane with _________ and _______
short c-terminal tails and Large N-terminal extra cellular domains.
Integrin: The intracellular tail of ___________ binds to a complex of proteins that form a linkage to cytoskeleton
Beta subunit
integrin: Intracellular linkage to actin is mediate by _______ and a set of other anchorage proteins
talin
Integrins signal bidirectionally: Information flow from extracellular stimuli to induce intracellular changes ( ), but intracellular stimuli can also cause extracellular changes ( ).
outside-in signaling…………. Inside-out signaling.
Focal contacts
sites where ECM, Integrins & cell cytoskeleton interact.
FAK:
Cytoplasmic Protein Tyrosine Kinase
- Recruited by talin or paxillin
- clustered FAK autophosphorylate providing docking site for Src-family kinases, leading to src activation.
**FAK and Src-family kinases cause outside in signaling.
Collagen
-Repeating triplet sequence
Gly-X-Y-Gly-X-Y-Gly-X-Y
- Triple Helix:
- -each chain is twisted to the left
- the chains helically twist around each other to the right.
Co-factors of prolyl/lysyl hydroxylaes
_Lysyl/prolyl hydroxylases add –OH groups for collagen assembly
ascorbate, Fe2+
After being secreted into the ECM, collagen molecules assemble into higher order polymers called
collagen fibrils.