Cell Biology 14 - Motility 1 st

1. Cell Biology 14- Motility 1st Sung Youn Lee, PhD. Student Veterinary collage, Room 320 02 450 3719, 016 293 6059 leevet@paran.com

3. Chemotaxis and Celluar Motility • The chemotactic molecule must be received by a cellular receptor, and this information must be tranduced across the plasma membrane • The key to understanding most of these processes appears to reside in the actin skeleton and the proteins and molecules that regulate its(actin skeleton) structure.

5. endothelium • Selectin(low)/ICAMs(high) • can be stimulated by cytokine in response to metabolites from pathogenic microbe • Neutrophil • Roll over • Glycoprotein / CD11/CD18(integrin) Extravasation of white blood cells requires a change in cell shape and expression of leukocyte adhesion molecules • Neutrophil in circulation  more solated • Neutrophil during movement  gelled, relaxed state, deformable. • Sol-to-Gel transformation

7. endothelium • Cellular retraction • endoCAM(CD31) • Stimulate the phosphorylation of serine residues  contrction of the actin skeleton  to loosen their junctional attachment • Neutrophil • Secrete thrombin • and histamine Extravasation of white blood cells requires a change in cell shape and expression of leukocyte adhesion molecules

8. Transmembrane proteins mediate specific types of interactions with vascular endothelial cells • Neutrophil surface is covered with many different kinds of integral membrane proteins (most of them are transmembrnae protein). • To attach to the vascular wall, WBCs use at least two types of adhesion molecules • Selectins • Integrins (more complex adhesion system) • Ex, CD11/CD18(neutrophil β2 integrin) – ICAM-1(endothelium) • The accumulation of a large focus of neutrophils constitutes the acute inflammatory infiltrate and, along with the extravasated blood proteins, is known as pus.

9. Transmembrane proteins mediate specific types of interactions with vascular endothelial cells • Eosinophil express β1 integrin VLA-4. • VLA-4 binds preferentially to VCAM-1 on endothelial cells. • Selective adhesions : Neutrophil (β2 integrin), Eosinophil(β1 integrin) • Occupation of the chemokine receptors leads to upregulation of the expression of genes encoding the ICAM or VCAM molecules, by this mechanism of regulated gene expression, the endothelium can control the quality and quantity of the ensuring inflammatory infiltrate.

11. Receptor sensitivity during chemotaxis must be constantly regulatedto allow the cell to adjust to ever-changing extracellular conditions • Cell adhesion must be precisely regulated. • Too much adhesion ; the cell will be stuck firmly in place • Too little adhesion ; the cell being unable to gain a propulsive advantage over its substrate • Inside-out signaling • Results from conformational changes (binding affinity change) a rising from within the cytoplasmic domain of integrin • Kinases, phospholipase, intracellular Ca2+, and G proteins • Ex, to neutralize the chemotaxic stimulus • The number of receptor▽ • To phosphorylate the intracellular domain of G-protein-coupled receptor  affinity for signal-blocking prtein△

12. The initiation of directed cellular migration requires the cell to polarize the cytoplasmic constituents and redistribute cell surface proteins • When migrating cells are viewed by phase microscopy, the cell is seen to extend a leading edge, or lamellipodium. Actin filaments are the major cytoskeletal element associated with the leading edge. • Continuous polymerization of new actin filament at the front • Depolymerization somewhere toward the center of the cells • Chemotaxic receptor of neutrophil • f-met receptor (the characteristic of bacterial protein; ATG start codon)

14. White blood cells can sense a chemical gradient and migrate toward ; Chemotaxtic Migration • 3 motions of non-muscle cells • 1st : random motion • 2nd : chemokinesis - rotation • 3rd : chemotaxis – toward the source of the chemical stimulus

15. The chemotactic signal is transduced across the cell membranein the form of calcium ions • In the case of neutrophil, concentration differences of as little as 1% are sufficient to elicit a chemotactic migration when ½ receptors are occupied. • ‘Limit of receptor number’ • Synthesize new receptors are inserted into the leading edge • Incorporation with secretion of azurophil granule • Recycle the receptors

16. The chemotactic signal is transduced across the cell membranein the form of calcium ions • The binding of chemotactic molecules • Induced chemotaxis • Induced others • the respiratory burst • the release of lysosomal enzymes • the production and release of arachidonic acid metabolite (cyclooxygenase-prostaglandins, lipooxygenase-leukotrienes) • There is a focal increase in Ca2+ -- activate --> phospholipase A2 –-convert --> PC to arachidonic acid (LTB4 – chemotactic molecule) -- secreted into extracellular space --> autocrine signaling

17. Thank you for your attention ~