Pkc
The catalytic domain of
overexpressed protein kinase C (PKC)-delta mediates phorbol 12-myristate
13-acetate (PMA)-induced differentiation or apoptosis in appropriate model cell
lines. To define the portions of the catalytic domain that are critical for
these isozyme-specific functions, we constructed reciprocal chimeras,
PKC-delta/epsilonV5 and -epsilon/deltaV5, by swapping the V5 domains of
PKC-delta and -epsilon. PKC-delta/epsilonV5 failed to mediate PMA-induced
differentiation of 32D cells, showing the essential nature of the V5 domain for
PKC-delta's functionality. The other chimera, PKC-epsilon/deltaV5, endowed
inactive PKC-epsilon with nearly all PKC-delta's apoptotic ability, confirming
the importance of PKC-delta in this function. Green fluorescent protein
(GFP)-tagged PKC-deltaV5 and -epsilon/deltaV5 in A7r5 cells showed substantial
basal nuclear localization, while GFP-tagged PKC-epsilon and -delta/epsilonV5
showed significantly less, indicating that the V5 region of PKC-delta contains
determinants critical to its nuclear distribution. PKC-epsilon/deltaV5-GFP
showed much slower kinetics of translocation to membranes in response to PMA
than parental PKC-epsilon, implicating the PKC-epsilonV5 domain in membrane
targeting. Thus, the V5 domain is critical in several of the isozyme-specific
functions of PKC-delta and -epsilon.
PMID: 14985469 [PubMed - in process]