PKC-mediated phosphorylation regulates c-FLIP ubiquitylation and stability

A1 Journal article (refereed)

Internal Authors/Editors

Publication Details

List of Authors: Kaunisto, Kochin, Asaoka, Mikhailov, Poukkula, Meinander, Eriksson
Publication year: 2009
Journal: Cell Death and Differentiation
Journal acronym: Cell Death Differ
Volume number: 16
Issue number: 9
Start page: 1215
End page: 1226
ISSN: 1350-9047
eISSN: 1476-5403


Cellular FLICE-inhibitory protein (c-FLIP) proteins are crucial regulators of the death-inducing signaling complex (DISC) and caspase-8 activation. To date, three c-FLIP isoforms with distinct functions and regulation have been identified. Our previous studies have shown that the stability of c-FLIP proteins is subject to isoform-specific regulation, but the underlying molecular mechanisms have not been known. Here, we identify serine 193 as a novel in vivo phosphorylation site of all c-FLIP proteins and demonstrate that S193 phosphorylation selectively influences the stability of the short c-FLIP isoforms, as S193D mutation inhibits the ubiquitylation and selectively prolongs the half-lives of c-FLIP short (c-FLIP(S)) and c-FLIP Raji (c-FLIP(R)). S193 phosphorylation also decreases the ubiquitylation of c-FLIP long (c-FLIP(L)) but, surprisingly, does not affect its stability, indicating that S193 phosphorylation has a different function in c-FLIP(L). The phosphorylation of this residue is operated by the protein kinase C (PKC), as S193 phosphorylation is markedly increased by treatment with 12-O-tetradecanoylphorbol-13-acetate and decreased by inhibition of PKCalpha and PKCbeta. S193 mutations do not affect the ability of c-FLIP to bind to the DISC, although S193 phosphorylation is increased by death receptor stimulation. Instead, S193 phosphorylation affects the intracellular level of c-FLIP(S), which then determines the sensitivity to death-receptor-mediated apoptosis. These results reveal that the differential stability of c-FLIP proteins is regulated in an isoform-specific manner by PKC-mediated phosphorylation.

Last updated on 2019-21-11 at 03:58