1. Cell Migration Tom Paine March 16, 2010

2. Will cover papers on single cell migration, adhesion- dependent trafficking and collective cell migration. Single Cell Migration Adhesion-Dependent Raft Trafficking Collective Cell Migration

3. Cell migration is a fundamental aspect of biology in both single and multi-cell organisms. Slime moldCancer Invasion Tissue Repair

4. Single Cell Migration

5. Cell migration is a cycle with 6 main steps. Sense stimulus Cell polarization and protrusion Attach to substrate Make room Contract Slide rear forward

6. Stimulus in form of chemo attractant gradient, involves signaling transduction. Signaling transduction sets up gradient. Different molecules active in front and back. Rho family GTPases, phosphoinositide 3 kinases, PI3ks, integrins, microtubules, vesicular transport

7. Polarization is mediated by Rho family proteins

8. Gradient Amplifiers PI3Ks and PTENs allow cells to respond directionally to very shallow chemoattractant gradients. Phosphoinositides PIP3 and PI(3,4)P2 rapid and highly polarized with chemo attractants PI3K localizes at leading edge Generates PIP3/PI(3,4)P2 Break these systems and cells can migrate but have problems moving up chemoattractant gradients

9. Cdc42 Active in front – If you inhibit it or turn it on everywhere, directionality of migration is hindered. Can move Microtubule Organizing Center (MTOC) and Golgi apparatus in front of the nucleus near the cell leading edge. – Position of MTOC maybe allow MT growth into the lamellipodia – Make it easier for Golgi derived vesicles to get to leading edge

10. GTP binding proteins It is activated by many chemoattractants It can help localize Cdc42 at leading edge Integrins may also contribute to localizing Cdc42 activation

11. Actin Filaments Regulations

14. Cell Migration Model

15. Integrins Protrusions must attach to surroundings – Act as the ‘feet’ Active integrins go to leading edge GTPase Rap 1 or PKC increase integrin affinity Cytoskeletal linker protein, talin promotes integrin activation Act as traction sites and mechano sensors

16. Rear end contraction So strong integrins may break off Can even activate stretch activated calcium channels

17. Adhesion Dependent Trafficking of Lipid Rafts

18. Lipid rafts contain GTPases such as Rac, Rho, and Cdc42. These are important in cell migration. In anchorage-dependent cells, loss of adhesion triggers cause raft compoent endocytosis. Rac1 and PI3K are down regulated. Paper further studies adhesion dependent endocytosis and exocytosis or raft components.

19. After detachment lipid rafts endocytosis and transport is actin and microtubule dependent.

20. Lipid rafts seem to be localized near gamma-tubulin, and the MTOC, but where specifically?

21. Experiment showed lipids rafts were actually in an area complimentary to the cis-Golgi marker.

22. Lipid rafts location constant, even when Golgi is dispersed by brefeldin A (BFA).

23. Lipid rafts also not localized to Smooth ER, as imaged by Autocrine motility factor receptor (AMF-R).

24. Also localized with Arf6, which regulates trafficking of Rac from recycling endosome to plasma membrane.

25. Lipid raft trafficking is dependent on actin, microtubules and Arf6.

26. Collective Cell Migration

27. Mechanisms of collective cell migration are similar to single cell migration, but split over many cells.

28. Collective cell migration has applications to morphogensis, tissue repair and cancer invasion.

29. More cells to work with Simultaneous coordinated polarization of many cells at leading edge Physical coupling drags cells forward Lamella at cells at leading edge and underneath cell collective More remodelling of migration track, to accommodate increased cell mass and volume Retraction of multiple cells at rear

30. Cell-cell interactions, both physical and chemical become important.

31. Interactions with the stroma can also affect collective cell migration.

32. Focalized proteolysis Lots of cells need room to move. Local matrix degradation and generation and widening of paths are important. Single cancer cells -> Small microtracks Collective cells -> macrotracks (100s of micrometers)

33. References Cell Migration: Integrating Signals from Front to Back – Ridley et al 2003 Arf6 and microtubules in adhesion-dependent trafficking of lipid rafts – Balasubramanian et al 2007 Mechanisms of collective cell migration at a glance – Ilina et al 2009

34. Questions?