Glycogen synthase kinase 3 (GSK3) was initially isolated as a critical protein in energy metabolism. However, subsequent studies indicate that GSK-3 is a multi-tasking kinase that links numerous signaling pathways in a cell and plays a vital role in the regulation of many aspects of cellular physiology. As a regulator of actin and tubulin cytoskeleton, GSK3 influences processes of cell polarization, interaction with the extracellular matrix, and directional migration of cells and their organelles during the growth and development of an animal organism. In this review, the roles of GSK3–cytoskeleton interactions in brain development and pathology, migration of healthy and cancer cells, and in cellular trafficking of mitochondria will be discussed.

Fructose 1,6-bisphosphatase 2 (Fbp2) is a gluconeogenic enzyme and multifunctional protein modulating mitochondrial function and synaptic plasticity via protein-protein interactions. The ability of Fbp2 to bind to its cellular partners depends on a quaternary arrangement of the protein. NAD⁺ and AMP stabilize an inactive T-state of Fbp2 and thus, affect these interactions. However, more subtle structural changes evoked by the binding of catalytic cations may also change the affinity of Fbp2 to its cellular partners. In this report, we demonstrate that Fbp2 interacts with Co²⁺, a cation which in excessive concentrations, causes pathologies of the central nervous system and which has been shown to provoke the octal-like events in hippocampal slices. We describe for the first time the kinetics of Fbp2 in the presence of Co²⁺, and we provide a line of evidence that Co²⁺ blocks the AMP-induced transition of Fbp2 to the canonical T-state triggering instead of a new, non-canonical T-state. In such a state, Fbp2 is still partially active and may interact with its binding partners e.g., Ca²⁺/calmodulin-dependent protein kinase 2α (Camk2α). The Fbp2-Camk2α complex seems to be restricted to mitochondria membrane and it facilitates the Camk2α autoactivation and thus, synaptic plasticity.

Fructose 1,6-bisphosphatase 2 (FBP2) is a multifunctional protein whose cellular functions depend on its oligomeric state. Forced FBP2 tetramerization has been linked to microtubule disruption and impaired mitochondrial trafficking, accompanied by abnormal mitochondrial morphology. Here, we identify MIC60 (mitofilin), a core element of the mitochondrial contact site and cristae organizing system (MICOS), as a potential mediator of these effects. Using proximity ligation assay, protein crosslinking combined with mass spectrometry, and ultrastructural analysis, we demonstrate that FBP2 is in close proximity to MIC60 under basal conditions and this proximity is reduced upon FBP2 tetramerization or partial FBP2 depletion. Loss of this proximity coincides with marked remodeling of inner-membrane ultrastructure. These findings are consistent with a working model in which dimeric FBP2 contributes to the coordination of microtubule-dependent mitochondrial positioning with MICOS-linked intramitochondrial organization, providing a plausible mechanistic bridge between metabolic cues (AMP/NAD⁺) and mitochondrial structural integrity.