1. P.R. Smith, Cell Biology - 2007 Skeletal Muscle Control

2. P.R. Smith, Cell Biology - 2007

4. from Gray’s Anatomy

5. P.R. Smith, Cell Biology - 2007 Neuromuscular Junctions Motor Nerve

6. P.R. Smith, Cell Biology - 2007 Junctional folds Nerve Terminal S

7. P.R. Smith, Cell Biology - 2007

8. Kessel/Kardon

9. P.R. Smith, Cell Biology - 2007 T-tubule Terminal Cisterna Calsequestrin Ryanodine receptor Dihydropyridine receptor Ryanodine receptor

10. P.R. Smith, Cell Biology - 2007 T-tubule Lumen Muscle sarcoplasm VV Ca 2+ T-T TC/SR Dihydropyridine receptor Ryanodine receptor Calsequestrin calcium ATPase

11. P.R. Smith, Cell Biology - 2007

12. Actin-Myosin Force-Generating Interaction Regulated by troponin-tropomyosin 1.[Ca ++ ].LT. 10 -7 M -- ATPase inhibited (  no cross-bridge cycling) 2.[Ca ++ ].GT. 10 -5 M -- ATPase not inhibited Typical of striated muscle.

13. P.R. Smith, Cell Biology - 2007 1 2 3 4

14. Actin-Myosin Interaction Cross-Bridge Cycling

15. P.R. Smith, Cell Biology - 2007 One Half of the Myosin Molecule

16. P.R. Smith, Cell Biology - 2007 Myosin Dimer

17. P.R. Smith, Cell Biology - 2007 Skeletal Muscle Thick Filament

18. P.R. Smith, Cell Biology - 2007 Woodhead el al. (2005) Nature, 436 1195

19. P.R. Smith, Cell Biology - 2007

20. (Kabsch et al. 1990)

21. P.R. Smith, Cell Biology - 2007 Visualizing Troponin In porcine cardiac muscle Spiess et al. (1999) JSB, 126, 98-104

22. P.R. Smith, Cell Biology - 2007 Myosin Tropomyosin Actin Metzger & Westfal, 2004 Troponin Complex (T,I,C) cf: Ross, p252

23. P.R. Smith, Cell Biology - 2007

24. Actin-Stimulated ATPase Activity - Actin : active - Actin + Trop : active - Actin + Trop + T T + T I : inhibited - Actin + Trop + T T + T I + T C : [Ca ++ ] regulated } [Ca ++ ] ind.

25. P.R. Smith, Cell Biology - 2007 Metzger & Westfal, 2004 Myosin S1

26. P.R. Smith, Cell Biology - 2007 Vale, Milligan and Johnson, 2000

27. P.R. Smith, Cell Biology - 2007 http://www.unmc.edu/Physiology/ Mann/mann14.html

28. P.R. Smith, Cell Biology - 2007 Cardiac Muscle

29. P.R. Smith, Cell Biology - 2007

30. from Gray’s Anatomy

31. P.R. Smith, Cell Biology - 2007 Smooth Muscle

32. P.R. Smith, Cell Biology - 2007

33. Sarcoplasmic Matrix

34. P.R. Smith, Cell Biology - 2007 Smooth Muscle Contraction Occurs in response to:- Nerve stimulation (autonomic) Mechanical stretching Hormones / Drugs

35. P.R. Smith, Cell Biology - 2007 Smooth Muscle Thin Filaments Thin filaments contain actin with tropomyosin, similar to striated muscle, BUT … 1. Different actin isoforms (  -vascular and  -enteric vs.  -skeletal,  -cardiac, and  -vascular;  -cytoplasmic; and  -cytoplasmic) 2. No troponin 3. Caldesmon 4. Calponin } Actin-based regulation?

36. P.R. Smith, Cell Biology - 2007 A. F-actin B. F-actin + calponin C. F-actin + tropomyosin D. F-actin + trop. + calp. F-actinF-actin + calponin Hodgkinson, et al., J. Mol. Biol. (1997) 273, 150-159

37. P.R. Smith, Cell Biology - 2007 Smooth Muscle Thick Filaments Skeletal Muscle

38. P.R. Smith, Cell Biology - 2007 Myosin-Based Regulation of ATPase Activity Two-step process: 1.Ca ++ -dependent kinase activated ([Ca ++ ] ≈ 10 -5 ) 2.Kinase phosphorylates myosin light chains: contraction 3.MLC phosphatase de-phosphorilates the MLC: relaxation The actin-stimulated myosin ATPase is inhibited If the myosin light chains are not phosphorylated. Typical of smooth muscle.

39. P.R. Smith, Cell Biology - 2007 Myosin-Based Regulation of ATPase Activity http://www.lib.mcg.edu/edu/eshuphysio/program/section2/2ch8/myosin.htm MLCK - myosin light chain kinase CM - Calmodulin

40. P.R. Smith, Cell Biology - 2007 Actin Filament Attachment

41. P.R. Smith, Cell Biology - 2007 Smooth Muscle Contraction S.J. Gunst, et al., 2003

42. P.R. Smith, Cell Biology - 2007 The End!

43. P.R. Smith, Cell Biology - 2007 Actin-Based Regulation of ATPase Activity Regulated by presence of troponin-tropomyosin: 1.[Ca ++ ].LT. 10 -7 M -- ATPase inhibited (  no cross-bridge cycling) 2.[Ca ++ ].GT. 10 -5 M -- ATPase not inhibited The actin-stimulated myosin ATPase is inhibited if the myosin light chains are not phosphorylated. Typical of smooth muscle.

44. P.R. Smith, Cell Biology - 2007 Smooth Muscle Functionally - Two types: 1.Multi-unit (e.g. papillary muscle in the eye, large blood vessel walls): Under nervous control (autonomic) Normally no spontaneous contractions No intercellular connections (gap junctions) 2.Single-unit / unitary (e.g. visceral) Spontaneous contractions (peristalsis) Many intercellular connections Characteristics: Cells typically small & spindle- shaped; central nucleus; “Smooth” appearance (no striations); Involuntary;