Project: Research project

Project Details


The protein kinase C enzyme family is involved in a number of cellular
functions, including the control of cellular proliferation and
differentiation. Human erythroleukemia (K562) cells express three PKC
isotypes, alpha PKC, betaII PKC and zeta PKC. These cells can be induced
to differentiate along the megakaryocytic pathway upon exposure to the PKC
activator phorbol myristate acetate e (PMA). Expression of the three PKC
isotypes are differentially regulated during PMA-induced cytostasis and
differentiation. Alpha and zeta PKC levels increase significantly and beta
II PKC levels fall dramatically upon PMA treatment. Therefore, alpha and
zeta PKC levels correlate with PMA-induced cytostasis and differentiation,
whereas beta II PKC levels correlate with the proliferative capacity of the
cells. In order to explore isotype-specific function, we assessed the
effect of overexpression and anti-sense inhibition of expression of the
alpha and beta II PKC isotypes on the proliferation and differentiation
potential of k562 cells. Over expression of alpha PKC leads to a gene
dose-dependent decrease in the rate of proliferation and increased
responsiveness to PMA whereas anti-sense inhibition of alpha PKC expression
leads to relative resistance to PMA-induced cytostasis. Conversely,
overexpression of betaII PKC leads to relative resistance to PMA-induced
cytostasis whereas anti-sense inhibition of beta II PKC expression blocks
K562 cell proliferation. these results indicate that alpha PKC is directly
involved in the cytostatic and differentiative effects of PMA whereas
betaII PKC is required for K562 cell proliferation. Through the use of
domain switch alpha beta II PKC chimera, we have identified regions on
alpha and beta II PKC required for isotype-specific function. The goals of
this proposal are to i) determine the role of zeta PKC in K562 cell
proliferation and differentiation through overexpression and anti-sense
inhibition of expression of the enzyme, ii) define minimal molecular
determinants capable of mediating the isotype specific functions of alpha
and beta II PKC in-vivo through expression of chimeric alpha beta II PKC in
K562 cells and iii) identify and characterize cellular proteins involved in
isotype-specific signal transduction in K562 cells through interactive
cloning strategies. Completion of these aims will provide important new
insight into the molecular basis for PKC isotype specific function in-vivo
and identify molecular targets for PKC isotype-specific signalling.
Furthermore, since anti-proliferative and differentiation therapy is an
important modality for the clinical treatment of human leukemia, the
proposed studies may identify molecular targets i human leukemic cells of
therapeutic importance.
Effective start/end date4/1/922/28/04


  • Medicine(all)