Related Experiment Video
Updated: Aug 11, 2026
Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development
Published on: June 15, 2017
A spatiotemporally coordinated cascade of protein kinase C activation controls isoform-selective translocation
Alejandra Collazos1, Barthélémy Diouf, Nathalie C Guérineau
1Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, F-34094 Montpellier Cedex 5, France.
Abstract:
In pituitary GH3B6 cells, signaling involving the protein kinase C (PKC) multigene family can self-organize into a spatiotemporally coordinated cascade of isoform activation. Indeed, thyrotropin-releasing hormone (TRH) receptor activation sequentially activated green fluorescent protein (GFP)-tagged or endogenous PKCbeta1, PKCalpha, PKCepsilon, and PKCdelta, resulting in their accumulation at the entire plasma membrane (PKCbeta and -delta) or selectively at the cell-cell contacts (PKCalpha and -epsilon). The duration of activation ranged from 20 s for PKCalpha to 20 min for PKCepsilon. PKCalpha and -epsilon selective localization was lost in the presence of Gö6976, suggesting that accumulation at cell-cell contacts is dependent on the activity of a conventional PKC. Constitutively active, dominant-negative PKCs and small interfering RNAs showed that PKCalpha localization is controlled by PKCbeta1 activity and is calcium independent, while PKCepsilon localization is dependent on PKCalpha activity. PKCdelta was independent of the cascade linking PKCbeta1, -alpha, and -epsilon. Furthermore, PKCalpha, but not PKCepsilon, is involved in the TRH-induced beta-catenin relocation at cell-cell contacts, suggesting that PKCepsilon is not the unique functional effector of the cascade. Thus, TRH receptor activation results in PKCbeta1 activation, which in turn initiates a calcium-independent but PKCbeta1 activity-dependent sequential translocation of PKCalpha and -epsilon. These results challenge the current understanding of PKC signaling and raise the question of a functional dependence between isoforms.
Insights
Thyrotropin-releasing hormone (TRH) triggers a sequential protein kinase C (PKC) cascade in pituitary cells. This organized PKC isoform activation controls cell signaling and protein localization, revealing new insights into PKC pathway regulation.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Signaling
Background:
- Protein Kinase C (PKC) signaling is crucial in cellular processes.
- PKC isoforms exhibit diverse roles and activation patterns.
- Understanding PKC spatiotemporal dynamics is key to elucidating cellular responses.
Purpose of the Study:
- To investigate the self-organization and spatiotemporal coordination of PKC isoform activation.
- To determine the sequential activation cascade and localization patterns of PKC isoforms following TRH receptor stimulation.
- To elucidate the functional dependence and regulatory relationships between different PKC isoforms.
Main Methods:
- Utilized pituitary GH3B6 cells expressing GFP-tagged or endogenous PKC isoforms.
- Stimulated cells with thyrotropin-releasing hormone (TRH) to activate TRH receptors.
- Employed pharmacological inhibitors (Gö6976), constitutively active/dominant-negative PKCs, and small interfering RNAs (siRNAs) to dissect signaling pathways.
- Monitored PKC localization and activation dynamics using fluorescence microscopy.
- Assessed beta-catenin relocation as a functional readout.
Main Results:
- TRH receptor activation initiated a sequential cascade: PKCbeta1 -> PKCalpha -> PKCepsilon.
- PKCbeta1 and PKCdelta accumulated at the plasma membrane, while PKCalpha and PKCepsilon localized to cell-cell contacts.
- PKCalpha localization depended on PKCbeta1 activity (calcium-independent), and PKCepsilon localization depended on PKCalpha activity.
- PKCdelta activation was independent of the PKCbeta1/alpha/epsilon cascade.
- PKCalpha, but not PKCepsilon, mediated TRH-induced beta-catenin relocation.
Conclusions:
- TRH receptor activation orchestrates a specific, self-organizing PKC isoform cascade in pituitary cells.
- Distinct PKC isoforms exhibit unique spatiotemporal activation and localization dynamics.
- The study reveals novel regulatory dependencies between PKC isoforms, challenging existing models of PKC signaling.
- PKCalpha plays a critical role in TRH-induced cellular events, while PKCepsilon's function may be more specialized.
Related Concept Videos
01:22Amplifying Signals via Enzymatic Cascade
01:07MAPK Signaling Cascades
01:16Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:25cAMP-dependent Protein Kinase Pathways
01:24Intracellular Signaling Cascades
01:24Intracellular Signaling Cascades