Transcription

1

2

3

4

5

6

7

8

9

10

11 Many Forms of Cell-Cell Communication Regulate Tissue Function and Phenotype

12 Physiological Functions of Gap Junctions Homeostasis buffering/sharing of ions, nutrients, and water Metabolic support nutrient transfer to avascular tissues Electrical coupling low-resistance synapses in neurons and muscle Embryogenesis transfer of morphogenic factors amongst cells in developmental fields Enhanced Tissue Response transfer of second messengers from stimulated to unstimulated cells Regulation of Cell Growth exchange of growth controlling signals between neighboring cells

13 Diseases Associated with Defective Gap Junctions Cardiac arhythmia Dysfunctional labor Hereditary deafness Peripheral neuropathy Cataracts Diabetes Infertility Teratogenesis Cancer

14 Most Neoplastic Cells have Decreased Gap Junction Expression and Function Rodent and human cell lines and tumor tissues. Causes: Decreased connexin gene expression. Improper connexin localization Poor cell-cell adhesion Altered regulation of GJ channel permeability Cx s are sensitive to phosphorylation, Ca +2, ph. src, neu, ras, MAPK, PKC close GJ channels.

15

16 P Rb E2F G 1 - Cyclin D1 CDK ATP + p27 P P Rb P P P ADP E2F E2F S-phase genes S

17 Mechanism of G 1 Growth Suppression: GJIC Buffers Low MW Regulators? * * ** * * OR * * * ** ** Reduced cell-cell contact No gap junctions 2- [*] 1-0- G 1 S G 2 M * G 1 inhibitor Threshold for S * * * * * * * GJIC present 2- [*] 1-0- G 1

18 Benefits of Enhanced GJIC/Cx Expression in Cancer Therapy GJIC with normal cells might decrease glutathione levels in tumor cells Increased GJIC/Cx expression decreases growth and tumorigenicity of cancer cells 1 2 GJIC might increase drug dispersal in poorly vascularized tumors BV BV GJIC improves the Bystander Effect GCV TK GCV-P TK+ DNA 3 4 Cell death

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66 Origin of Two Types of GJIC Deficient Tumor Cells: Hypothesis Transitional Cell Contact inhibited by GJ s differentiated cell Induced GJ s Stem Cell No expressed GJ s GJIC + partially differentiated cells, [GJIC+] GJIC - INITIATION PROMOTION blocks GJIC GJIC - GJIC - Growth inhibited by negative growth suppressors blocks (-) growth regulators Tumor Cell GJIC- (eosinophilic) PROGRESSION Tumor Cell GJIC- (basinophilic)

67 is Senescence Gap Junctions in Cellular Homeostasis = intercellular signal Toxic Chemicals 8 8 is receptor Biological End Points Cell Apoptosis proliferation Cell Adaptive responses of Differentiation differentiated cells Distal cell Growth factor Extracellular Communication Translational Regulators Transcriptional Regulators Post translational Regulators Intracellular Communication Intercellular Communication (Upham et al, 1998)

68

69 H 2 O 2, EGF PDGF T R K Mitogen Activated Protein Kinase- Signal Transduction (ERK) SHHS T R SH HS K GRB2 msos Ras Cell proliferation Cell differentiation GTP GDP transcription translation TF TF-Pi ERK ERK-Pi Raf Raf-Pi MEK MEK-Pi TF = transcription factor

70 Restoration of normal GJIC in WB ras cells grown in psyllium for 48h CH 3 CN control EtOH control Crude (1.5 mg/ml) EtOH extract (50 µg/ml)

71 The Effect of Psyllium on GJIC in ras WB-cells GJIC (Fraction of the Control) Dose (µg/ml)

72 Effect of psyllium on the phosphorylation of Cx43 in the ras-transfected WB cell line WB WB-ras Psyllium (µg/ml): Cx43: Treatment time: 48 h

73 The largest AIG + colony of WB ras cell grown with psyllium for 21 days Control 25 µg/ml 37.5 µg/ml 50 µg/ml 75 µg/ml

74 Anchorage Independent Growth Colonies Formed (% of the Control) (control ave = 128) EtOH Extract of Psyllium Dose (µg/ml)

75 Ras localization with EtOH extract from Psyllium seed husk in WB ras for 48h treatment 0 -Prim ab. WB 25 µg/ml

76 Relative Density of Gel Bands ratio m-p21 ras p-p21 ras 90 membrane 60 cytosolic Psyllium (µg/ml) Ratio of p21 ras (m:p)

77 Cx 43 localization with EtOH extract from Psyllium seed husk in WB ras cells treated for 48 h WB + Cx43 peptide -Prim. ab. WB ras -Prim ab. WB-ras WB-ras WB-ras WB-ras Psyllium dose (µg/ml)

78 Effect of psyllium on ERK in both the wild-type and rastransfected WB cell line WB WB-ras Psyllium (µg/ml): ERK p44 p42 Treatment time: 48 h

79

80

81