2. Interact with myosin proteins

3. Myosin I

4. Myosin II

5. Globular heads interact with actin

6. Light chains regulate ATP hydrolysis

7. Types of actin filament protein connections

8. Capping proteins

9. Cross-linking

10. Severing

11. Mono-sequestering

12. Bundling

13. Important in filopodia

14. Drugs that affect actin filaments and microtubules

15. Some stabilize

16. Some cap

17. Prevent polymerization

18. Cell movement with actin

19. Interact with myosin proteins (we will focus on myosin I)

20. Slide 25

21. When gloubular heads bind to actin filaments, which is a wound structure, the heads interact with the actin monomers and the head bends/moves, which causes the actin filaments to bend in, towards the minus end. This shortens the length of the sarcomere

22. Myosin II is involved in cell-splitting

23. Myosin I

24. A family of proteins that does more for allowing the forward movement of cells and it also transports vesicles along actin filaments. It moves toward the + end.

25. Myosin IV moves toward the – end.

26. Slide 28

27. + ends are usually toward -the plasma membrane

28. Slide 29

29. There are steps to cell movement:

30. Formation of leading edge, protrusion of lamellipodia and filopodia

31. (red spots under cell adhere to filaments on the substratume, myosin I)

32. cytoplasmic streaming from back to front of cell.

33. Severing at the back of the cell and contraction of actin filaments. (myosin II)

34. Focal adhesions are dependent on forward movement

35. They require the actin filament, and its polymerization, the adhesion to myosin I, and it requires the transmembrane proteins, the integrins, that link actin and myosin to the substrate on which the cell is growing.

36. Slide 30

37. Cap proteins helps stabilize actin meshwork.

38. Nucleation proteins, such as ARP2/3

39. Works with WASP protein

40. Wiskott Aldrich Syndrome - autosomal recessive condition seen in males more, associated with mutation in WASP protein, which works with ARP2/3 allows actin nucleation. Immune system abnormalities because the cells can’t migrate. Increased risks of cancer or infection. Red blood cells are low.

41. Nucleation is important for migration!

42. Slide 31

43. Retrograde flow of actin as actin head undergoes atp hydrolysis.

44. Transmembrane receptors bind to proteins in the substrate as well as actin associated proteins. When myosin 1 undergoes attachment to actin, that retrograde flow is translated to forward movement.

45. Slide 32

46. Rho proteins – all GTP binding proteins

47. Rho Family

48. They regulate actin dynamics

49. They all are active when bound to GTP and inactive when bound to GDP

50. GEFs strip off GDP and allow GTP to bind in G protein binding site.

51. Act as molecular switch

52. Rho

53. Activated Rho generated stress fibers in cell.

54. Used to make a rigid state in cell

55. Rac

56. Activated Rac caused ruffling of lamellipodia

57. Involved in lamilipodia formation

58. Cdc42

59. Formation of filopodia at peripheri of the cell