Biomedical subjects

Kateryna Kolkova

Publications and source records attributed to Kateryna Kolkova.

7 recordsLinked to original sources

PubMed2006

GAP-43 regulates NCAM-180-mediated neurite outgrowth.

The neural cell adhesion molecule (NCAM), and the growth-associated protein (GAP-43), play pivotal roles in neuronal development and plasticity and possess interdependent functions. However, the mechanisms underlying the functional association of GAP-43 and NCAM have not been elucidated. In this study we show that (over)expression of GAP-43 in PC12E2 cells and hippocampal neurons strongly potentiates neurite extension, both in the absence and in the presence of homophilic NCAM binding. This potentiation is crucially dependent on the membrane association of GAP-43. We demonstrate that phosphorylation of GAP-43 by protein kinase C (PKC) as well as by casein kinase II (CKII) is important for the NCAM-induced neurite outgrowth. Moreover, our results indicate that in the presence of GAP-43, NCAM-induced neurite outgrowth requires functional association of NCAM-180/spectrin/GAP-43, whereas in the absence of GAP-43, the NCAM-140/non-receptor tyrosine kinase (Fyn)-associated signaling pathway is pivotal. Thus, expression of GAP-43 presumably acts as a functional switch for NCAM-180-induced signaling. This suggests that under physiological conditions, spatial and/or temporal changes of the localization of GAP-43 and NCAM on the cell membrane may determine the predominant signaling mechanism triggered by homophilic NCAM binding: NCAM-180/spectrin-mediated modulation of the actin cytoskeleton, NCAM-140-mediated activation of Fyn, or both.

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PubMed2005

Triple effect of mimetic peptides interfering with neural cell adhesion molecule homophilic cis interactions.

The neural cell adhesion molecule (NCAM) is pivotal in neural development, regeneration, and learning. Here we characterize two peptides, termed P1-B and P2, derived from the homophilic binding sites in the first two N-terminal immunoglobulin (Ig) modules of NCAM, with regard to their effects on neurite extension and adhesion. To evaluate how interference of these mimetic peptides with NCAM homophilic interactions in cis influences NCAM binding in trans, we employed a coculture system in which PC12-E2 cells were grown on monolayers of fibroblasts with or without NCAM expression and the rate of neurite outgrowth subsequently was analyzed. P2, but not P1-B, induced neurite outgrowth in the absence of NCAM binding in trans. When PC12-E2 cells were grown on monolayers of NCAM-expressing fibroblasts, the effect of both P1-B and P2 on neurite outgrowth was dependent on peptide concentrations. P1-B and P2 acted as conventional antagonists, agonists, and reverse agonists of NCAM at low, intermediate, and high peptide concentrations, respectively. The demonstrated in vitro triple pharmacological effect of mimetic peptides interfering with the NCAM homophilic cis binding will be valuable for the understanding of the actions of these mimetics in vivo.

Amino Acid Sequence↗

PubMed2005

Distinct roles of PKC isoforms in NCAM-mediated neurite outgrowth.

The role of protein kinase C (PKC) isoforms in the neural cell adhesion molecule (NCAM)-mediated neurite outgrowth was tested using a co-culture system consisting of fibroblasts with or without NCAM expression upon which either primary cerebellar granular neurones (CGN) or pheochromocytoma (PC12-E2) cells were grown. The latter transiently expressed various PKC isoforms and domains derived from selected PKCs. PKC inhibitors of various specificity inhibited NCAM-stimulated neuritogenesis from CGN, indicating that PKC is involved in this process. Moreover, stimulation by the NCAM-mimetic peptide, C3d, elicited phosphorylation of PKC in CGN. Expression of kinase-deficient forms of PKCalpha, betaI and betaII blocked NCAM-mediated neurite extension, but had no effect on nerve growth factor (NGF)-mediated neurite outgrowth. Expression of two PKCepsilon constructs: (i) a fragment from PKCepsilon encompassing the pseudosubstrate, the C1a domain (including the actin-binding site, ABS), and parts of the V3 region, or (ii) the PKCepsilon-specific ABS blocked NCAM-mediated neurite extension in both cases. These two constructs also partially inhibited NGF-stimulated neuritogenesis indicating that PKCepsilon is a positive regulator of both NCAM- and NGF-mediated differentiation. We suggest that PKCepsilon is a common downstream mediator for several neuritogenic factors, whereas one or more conventional PKCs are specifically involved in NCAM-stimulated neurite outgrowth.

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PubMed2004

Zippers make signals: NCAM-mediated molecular interactions and signal transduction.

The neural cell adhesion molecule, NCAM, is involved in multiple cis- and trans-homophilic interactions (NCAM binding to NCAM) thereby facilitating cell-cell adhesion through the formation of zipper-like NCAM-complexes. NCAM is also involved in heterophilic interactions with a number of proteins and extracellular matrix molecules. Some of these heterophilic interactions are mutually exclusive, and some interfere with or are dependent on homophilic NCAM interactions. Furthermore, both homo- and heterophilic interactions are modulated by posttranslational modifications of NCAM. Heterophilic NCAM-interactions initiate several intracellular signal transduction pathways ultimately leading to biological responses involving cellular differentiation, proliferation, migration and survival. Both homo- and heterophilic NCAM-interactions can be mimicked by synthetic peptides, which can induce NCAM-like signalling, and in vitro and in vivo studies suggest that such NCAM mimetics may be used for the treatment of neurodegenerative disorders.

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PubMed2003

Structure and interactions of NCAM Ig1-2-3 suggest a novel zipper mechanism for homophilic adhesion.

The neural cell adhesion molecule, NCAM, mediates Ca(2+)-independent cell-cell and cell-substratum adhesion via homophilic (NCAM-NCAM) and heterophilic (NCAM-non-NCAM molecules) binding. NCAM plays a key role in neural development, regeneration, and synaptic plasticity, including learning and memory consolidation. The crystal structure of a fragment comprising the three N-terminal Ig modules of rat NCAM has been determined to 2.0 A resolution. Based on crystallographic data and biological experiments we present a novel model for NCAM homophilic binding. The Ig1 and Ig2 modules mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), whereas the Ig3 module mediates interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions) through simultaneous binding to the Ig1 and Ig2 modules. This arrangement results in two perpendicular zippers forming a double zipper-like NCAM adhesion complex.

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PubMed2003

The role of phosphatidylinositol 3-kinase in neural cell adhesion molecule-mediated neuronal differentiation and survival.

The neural cell adhesion molecule, NCAM, is known to stimulate neurite outgrowth from primary neurones and PC12 cells presumably through signalling pathways involving the fibroblast growth factor receptor (FGFR), protein kinase A (PKA), protein kinase C (PKC), the Ras-mitogen activated protein kinase (MAPK) pathway and an increase in intracellular Ca2+ levels. Stimulation of neurones with the synthetic NCAM-ligand, C3, induces neurite outgrowth through signalling pathways similar to the pathways activated through physiological, homophilic NCAM-stimulation. We present here data indicating that phosphatidylinositol 3-kinase (PI3K) is required for NCAM-mediated neurite outgrowth from PC12-E2 cells and from cerebellar and dopaminergic neurones in primary culture, and that the thr/ser kinase Akt/protein kinase B (PKB) is phosphorylated downstream of PI3K after stimulation with C3. Moreover, we present data indicating a survival-promoting effect of NCAM-stimulation by C3 on cerebellar and dopaminergic neurones induced to undergo apoptosis. This protective effect of C3 included an inhibition of both DNA-fragmentation and caspase-3 activation. The survival-promoting effect of NCAM-stimulation was also shown to be dependent on PI3K.

Amino Acid Sequence↗

PubMed2002

NCAM regulates cell motility.

Cell migration is required during development of the nervous system. The regulatory mechanisms for this process, however, are poorly elucidated. We show here that expression of or exposure to the neural cell adhesion molecule (NCAM) strongly affected the motile behaviour of glioma cells independently of homophilic NCAM interactions. Expression of the transmembrane 140 kDa isoform of NCAM (NCAM-140) caused a significant reduction in cellular motility, probably through interference with factors regulating cellular attachment, as NCAM-140-expressing cells exhibited a decreased attachment to a fibronectin substratum compared with NCAM-negative cells. Ectopic expression of the cytoplasmic part of NCAM-140 also inhibited cell motility, presumably via the non-receptor tyrosine kinase p59(fyn) with which NCAM-140 interacts. Furthermore, we showed that the extracellular part of NCAM acted as a paracrine inhibitor of NCAM-negative cell locomotion through a heterophilic interaction with a cell-surface receptor. As we showed that the two N-terminal immunoglobulin modules of NCAM, which are known to bind to heparin, were responsible for this inhibition, we presume that this receptor is a heparan sulfate proteoglycan. A model for the inhibitory effect of NCAM is proposed, which involves competition between NCAM and extracellular components for the binding to membrane-associated heparan sulfate proteoglycan.

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