M-phase-specific phosphorylation and structural rearrangement of the cytoplasmic cross-linking protein plectin involve p34cdc2 kinase.

Abstract

Plectin, a widespread and abundant cytoskeletal cross-linking protein, serves as a target for protein kinases throughout the cell cycle, without any significant variation in overall phosphorylation level. One of the various phosphorylation sites of the molecule was found to be phosphorylated preferentially during mitosis. By in vivo phosphorylation of ectopically expressed plectin domains in stably transfected Chinese hamster ovary cells, this site was mapped to the C-terminal repeat 6 domain of the polypeptide. The same site has been identified as an in vitro target for p34cdc2 kinase. Mitosis-specific phosphorylation of plectin was accompanied by a rearrangement of plectin structures, changing from a filamentous, largely vimentin-associated state in interphase to a diffuse vimentin-independent distribution in mitosis as visualized by immunofluorescence microscopy. Subcellular fractionation studies showed that in interphase cells up to 80% of cellular plectin was found associated with an insoluble cell fraction mostly consisting of intermediate filaments, while during mitosis the majority of plectin (> 75%) became soluble. Furthermore, phosphorylation of purified plectin by p34cdc2 kinase decreased plectin's ability to interact with preassembled vimentin filaments in vitro. Together, our data suggest that a mitosis-specific phosphorylation involving p34cdc2 kinase regulates plectin's cross-linking activities and association with intermediate filaments during the cell cycle.

Naringin-sensitive Phosphorylation of Plectin, a Cytoskeletal Cross-linking Protein, in Isolated Rat Hepatocytes

“…For example, plectin can be phosphorylated at Thr 4542 by the cyclin-dependent protein kinase CDK1/Cdc2 during mitosis, causing it to dissociate from vimentin filaments (64,65). Since plectin phosphorylation in the present study was detected by an anti-phosphothreonine antibody, it is clear that the toxin-sensitive phosphorylation site must likewise be a threonine.…”

Induction of rapid and reversible cytokeratin filament network remodeling by inhibition of tyrosine phosphatases

“…Interestingly, plectin affects assembly properties of both unassembled and assembled IF polypeptides, including CKs, in a complex fashion (Steinböck et al, 2000). Furthermore, plectin is subject to dynamic phosphorylation, most notably during M phase, when increased p34 cdc2 kinase-mediated phosphorylation of plectin is accompanied by its redistribution from a mostly filament-associated to a diffuse state (Foisner et al, 1996). The observed colocalisation of plectin with OVinduced CK granules was specific, since other CK-associated proteins, such as the desmosomal proteins desmoplakin and plakophilin (data not shown) and the signalling molecules of the 14-3-3 type did not co-distribute.…”

“…Phosphorylation may affect CK organization in a number of different ways: it leads to a shift in the equilibrium between the soluble and filamentous state toward the soluble form ; it may directly induce filament disassembly as suggested by in vitro experiments (Yano et al, 1991); and it alters the interaction with IFAPs, as demonstrated for the binding to the signaling 14-3-3 proteins, which act as solubility factors for CKs (Liao and Omary, 1996;Ku et al, 1998). Furthermore, phosphorylation of the cytoskeletal crosslinker plectin may affect CK organisation, as has been shown for plectin-lamin-B and plectin-vimentin interactions (Foisner et al, 1991;Foisner et al, 1996).…”

Identification of a novel cDNA, encoding a cytoskeletal associated protein, differentially expressed in diffuse large B cell lymphomas

“…It is now clear that the cytoskeleton, beside its structural role, is a highly dynamic structure, involved in cellular shape, mobility and division, but also in transduction and integration of transmembrane signals (Tapon and Hall, 1997;Yamada and Geiger, 1997), progression through the cell cycle (Assoian and Zhu, 1997) and mRNAs transport (Bassell and Singer, 1997). Since the dynamic properties of cytoskelal ®laments appear highly regulated by the phosphorylation state of cytoskeletal associated proteins (Foisner et al, 1996;Moon and Drubin, 1995), it is of interest that LB1 ORF contains numerous PKC and CKII phosphorylation sites. Besides, malignant transformation is characterized by disruption of cytoskeletal organization, altered adhesion-dependent responses and deregulated expression of cytoskeletal associated proteins (Ben-Ze'ev, 1997).…”