Cell junction & Junctional complexes

Review of Cell junction & Junctional complexes of the epithelial cells

1. Cell Junctions

2. Objectives Different types of cell junctions Functions of different types of cell junctions

3. C onnection between the neighboring cells o r contact between cell and extracellular matrix Cell junction

4. Basal domain Lateral domain Apical domain

5. Zonula occludens/ Tight junction Zonula adherens/ Adherent junction Macula adherens/ Desmosome Gap junction Hemidesmosome

6. Zonula occludens Zonula adherens Macula adherens Gap junction

7. Belt Something that occludes Something that adheres Spot Desmos - bond Soma- body Zonula occludens (tight junction) Zonula adherens Macula adherens (desmosome)

8. Zonula occludens

9. Also called tight junction Most apical of the junctions A continuous ribbon-like structure Forms a seal between adjacent cells Zonula occludens (contd.)

10. Zonula occludens (contd.)

11. Zonula occludens (contd.)

12. Zonula occludens (contd.)

13. Seals adjacent cells to one another Controls passage of molecules between cells Separate apical and basolateral membrane domain Forms different blood barrier Zonula occludens (contd.)

14. Zonula occludens (contd.) Blood-brain barrier

15. Zonula occludens (contd.) Blood- thymic barrier Tight junction Reticulo -epithelial cell Enothelial cell

16. Zonula occludens (contd.) Blood-testis barrier

17. Zonula occludens (contd.) Blood-CSF barrier

18. Zonula adherens

19. Also called adherent junction Immediately below zonula occludens Also encircles epithelial cells Firmly anchor a cell to its neighbor cells Zonula adherens (contd.)

20. Zonula adherens (contd.)

21. Zonula adherens (contd.)

22. Provide point linking to the cytoskeleton of adjacent cells Strengthen and stabilizes nearby tight junction Zonula adherens (contd.)

23. Macula adherens

24. Also called desmosome In lateral domain of cell membrane Does encircles epithelial cells Macula adherens (contd.)

25. Macula adherens (contd.)

26. Macula adherens (contd.)

27. Provide point of strong intermediate filament coupling between adjacent cells Strengthen the tissue Macula adherens (contd.)

28. Macula adherens (contd.) Macula adherens in skin

29. Gap junction

30. A communicating junction In lateral domain of cell membrane Permit exchange of molecules and ions Gap junction (contd.)

31. Gap junction (contd.)

32. Gap junction (contd.)

33. Allows direct transport of small molecules and ions from one cell to another Gap junction (contd.)

34. Hemidesmosome

35. Anchoring junction In basal domain of cell membrane Resembles half desmosome Hemidesmosome (contd.)

36. Hemidesmosome (contd.)

37. Hemidesmosome (contd.)

38. Anchor cytoskeleton of cell to the basal lamina Hemidesmosome (contd.)

39. Points Zonula occludens Zonula adherens Macula adherens Hemidesmosome Gap junction Major transmembr-ane protein Occludin , claudin and junctional adhesion molecules E- cadherin , catenin complexes Desmoglein and desmocollin Integrins Connexin Cytoskeletal components Actin filaments Actin filaments Intermediate filaments Intermediate filaments None Channel protein Absent Absent Absent Absent Present Communication Not possible Not possible Not possible Not possible Possible Function Acts as a barrier Adheres the adjacent cells Provides strong attachments between two cells Adheres the cell to the basal lamina Allows direct transmission of small molecules Summary

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