Studies have shown that treatment of intact cells with tumor promoters (TPA), as well as with certain growth factors and hormones, causes a rapid redistribution or stabilizaton (activation) of protein kinase C to the particulate fraction. Results indicate that part of the PK-C stabilized to the membrane fraction with exposure to tumor promoters may be recovered associated with nuclear-cytoskeletal components. Following treatment of NIH 3T3 cells with TPA for 20 min, PK-C activity is found tightly associated with the highly purified nuclear fraction. Immunohistochemical localization studies further support the observation that TPA treatment mediates association of PK-C to the nucleus and cytoskeleton of NIH 3T3 cells. This TPA-induced redistribution of PK-C to the nuclear fraction is not observed with HL-60 cells. The different subcellular ditributions of PK-C induced by TPA with different cell types may help to explain, in part, the different responses noted with various cell types with exposure to TPA. The same type of TPA-induced association of PK-C with membranes can be obtained in a reconstitution system with purified PK-C and isolated plasma membranes in the presence of TPA, Ca2+, and phosphatidylserine. This TPA mediated binding is dependent upon Ca2+, is time and temperature dependent, and reaches saturation at about 245 ng PK-C/mg PYS cell membrane protein. NIH 3T3 cells transformed with Kirsten (Ki) murine sarcoma virus have elevated membrane-associated PK-C activity and increased phosphatidylinositol (PI) metabolism relative to control 3T3 cells. In vitro studies with membranes isolated from NIH 3T3 and Ki-3T3 cells indicate PIP2-phosphodiesterase activity is increased with Ki-SV transformation of NIH 3T3 cells. The PIP2-PDE enzyme from Ki-3T3 cells also is more responsive to activation by GPT analogues. These results further support the suggestion for the involvement of PK-C activation (membrane association) in regulating cell proliferation, and in tumor promotion and malignant transformation, and also suggest possible modulation of this membrane signal transmission system by ras p21 protein.

Agency
National Institute of Health (NIH)
Institute
Division of Cancer Biology And Diagnosis (NCI)
Type
Intramural Research (Z01)
Project #
1Z01CB009015-03
Application #
3963059
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
3
Fiscal Year
1986
Total Cost
Indirect Cost
Name
Cancer Biology and Diagnosis
Department
Type
DUNS #
City
State
Country
United States
Zip Code