Protein Kinase Cα Promotes Proliferation and Migration of Schwann Cells by Activating ERK Signaling Pathway

Recent advances in PKC inhibitor development: Structural design strategies and therapeutic applications

Protein kinase C (PKC) isozymes play critical roles in diverse cellular processes and are implicated in numerous diseases, including cancer, diabetes, and autoimmune disorders. Despite extensive research efforts spanning four decades, only one PKC inhibitor has received clinical approval, highlighting the challenges in developing selective and efficacious PKC-targeting therapeutics. Here we review recent advances in the development of small-molecule PKC inhibitors, focusing on structural design strategies, pharmacological activities, and structure-activity relationships. We analyze emerging approaches including fragment-based drug design, allosteric targeting, and natural product derivatization that have yielded promising new scaffold classes. Special attention is given to innovations in achieving isozyme selectivity, particularly for PKCα and PKCβ, which have proven crucial for therapeutic applications. We discuss how integration of computational methods, structural biology insights, and rational design principles has advanced our understanding of PKC inhibition mechanisms. This comprehensive analysis reveals key challenges in PKC drug development, including the need for enhanced selectivity and reduced off-target effects, while highlighting promising directions for future therapeutic development. Our findings provide a framework for designing next-generation PKC inhibitors with improved clinical potential.

Targeted shortwave diathermy combined with perceptual training for patients with severe traumatic optic neuropathy

BACKGROUND

Patients with severe traumatic optic neuropathy (TON) often show limited improvement in visual function despite therapy.

OBJECTIVE

This study aims to investigate whether targeted shortwave diathermy (SWD) combined with perceptual training enhances visual function in patients with severe TON following endoscopic optic nerve decompression (EOND) surgery.

METHODS

Forty patients with severe TON after EOND surgery were randomly assigned to either the rehabilitation (Reh) group (n = 24) or the non-rehabilitation (Nreh) group (n = 16). Subjects in the Reh group received targeted SWD therapy and perceptual training. Visual function, visual evoked potentials, and diffusion tensor imaging were evaluated.

RESULTS

After 16 weeks of rehabilitation, the best-corrected visual acuity (p = 0.006) and color vision scores (p = 0.026) in the Reh group improved significantly more than those in the Nreh group. Two children who had completely lost their visual acuity 62 and 73 days after experiencing TON regained visual acuity scores of 1.0 logMAR or lower after rehabilitation. After 10 weeks of rehabilitation, the mean P100 amplitude (p = 0.012) and fractional anisotropy (anterior segment, p = 0.032; middle segment, p = 0.014) of the affected nerves in the Reh group were significantly higher than those in the Nreh group.

CONCLUSIONS

Targeted SWD combined with perceptual training demonstrated beneficial effects in patients with severe TON after EOND surgery. Notably, this study provides the first evidence of visual function recovery occurring 73 days after complete vision loss in child with TON when combined rehabilitation was implemented.

Efficacy and mechanisms of concentrated growth factor on facial nerve rehabilitation in a rabbit model

Accelerated rehabilitation following facial nerve injury presents unique clinical challenges. This study evaluates the therapeutic effects of concentrated growth factor (CGF) on facial nerve recovery in a rabbit model and on RSC96 Schwann cells. Characterization of the CGF membrane (CGFM) revealed a three-dimensional fibrin network with embedded platelets, and representative growth factors, including TGF-β1, PDGF-BB, IGF-1, bFGF, and VEGF, were detected. In vivo, the Crush + CGFM group exhibited enhanced axon and myelin regeneration, increased Schwann cell proliferation, and improved facial nerve function compared to the Crush group. In vitro, CGF treatment significantly promoted the proliferation and migration of RSC96 cells and facilitated axon elongation in NG108-15 cells compared to controls. Mechanistically, CGF treatment led to a significant increase in PDGFRβ phosphorylation. Inhibition of this pathway with SU16f decreased Schwann cell activity and hindered overall nerve rehabilitation. These results underscore CGF's potential to accelerate nerve repair by promoting axon and myelin regeneration and enhancing Schwann cell biological activity, with the PDGFRβ pathway playing a crucial regulatory role. This study highlights CGF as a promising therapeutic strategy for improving facial nerve rehabilitation.

α7 Nicotinic Acetylcholine Receptors May Improve Schwann Cell Regenerating Potential via Metabotropic Signaling Pathways

BACKGROUND

Schwann cells (SCs) are glial cells involved in peripheral axon myelination. SCs also play a strategic role after peripheral nerve injury, regulating local inflammation and axon regeneration. Our previous studies demonstrated the presence of cholinergic receptors in SCs. In particular, the α7 nicotinic acetylcholine receptors (nAChRs) are expressed in SCs after peripheral axotomy, suggesting their involvement in the regulation of SC-regenerating properties. To clarify the role that α7 nAChRs may play after peripheral axon damage, in this study we investigated the signal transduction pathways triggered by receptor activation and the effects produced by their activation.

METHODS

Both ionotropic and metabotropic cholinergic signaling were analyzed by calcium imaging and Western blot analysis, respectively, following α7 nAChR activation. In addition, the expression of c-Jun and α7 nAChRs was evaluated by immunocytochemistry and Western blot analysis. Finally, the cell migration was studied by a wound healing assay.

RESULTS

Activation of α7 nAChRs, activated by the selective partial agonist ICH3, did not induce calcium mobilization but positively modulated the PI3K/AKT/mTORC1 axis. Activation of the mTORC1 complex was also supported by the up-regulated expression of its specific p-p70 S6KThr389 target. Moreover, up-regulation of p-AMPKThr172, a negative regulator of myelination, was also observed concomitantly to an increased nuclear accumulation of the transcription factor c-Jun. Cell migration and morphology analyses proved that α7 nAChR activation also promotes SC migration.

CONCLUSIONS

Our data demonstrate that α7 nAChRs, expressed by SCs only after peripheral axon damage and/or in an inflammatory microenvironment, contribute to improve the SCs regenerating properties. Indeed, α7 nAChR stimulation leads to an upregulation of c-Jun expression and promotes Schwann cell migration by non-canonical pathways involving the mTORC1 activity.

Direct Current Electric Field Coordinates the Migration of BV2 Microglia via ERK/GSK3β/Cofilin Signaling Pathway

Direct current electric field (DCEF) steers the migration of various neural cells. Microglia, as macrophage of the central nervous system (CNS), however, have not been reported to engage in electrotaxis. Here, we applied electric fields to an in vitro environment and found directional migration of BV2 microglia toward the cathode, in a DCEF strength-dependent manner. Transcriptome analysis then revealed significant changes in the mitogen-activated protein kinase cascades. In terms of mechanism, DCEF coordinated microglia movement by regulating the ERK/GSK3β/cofilin signaling pathway, and PMA (protein kinase C activator) reversed cell migration through intervention of the ERK/GSK3β/cofilin axis. Meanwhile, LiCl (GSK3β inhibitor) showed similar functions to PMA in the electrotaxis of microglia. Furthermore, pharmacological and genetic suppression of GSK3β or cofilin also modulated microglia directional migration under DCEF. Collectively, we discovered the electrotaxis of BV2 microglia and the essential role of the ERK/GSK3β/cofilin axis in regulating cell migration via modulation of F-actin redistribution. This research highlights new insight toward mediating BV2 directional migration and provides potential direction for novel therapeutic strategies of CNS diseases.

Identification of key genes involved in axon regeneration and Wallerian degeneration by weighted gene co-expression network analysis

Peripheral nerve injury repair requires a certain degree of cooperation between axon regeneration and Wallerian degeneration. Therefore, investigating how axon regeneration and degeneration work together to repair peripheral nerve injury may uncover the molecular mechanisms and signal cascades underlying peripheral nerve repair and provide potential strategies for improving the low axon regeneration capacity of the central nervous system. In this study, we applied weighted gene co-expression network analysis to identify differentially expressed genes in proximal and distal sciatic nerve segments from rats with sciatic nerve injury. We identified 31 and 15 co-expression modules from the proximal and distal sciatic nerve segments, respectively. Functional enrichment analysis revealed that the differentially expressed genes in proximal modules promoted regeneration, while the differentially expressed genes in distal modules promoted neurodegeneration. Next, we constructed hub gene networks for selected modules and identified a key hub gene, Kif22, which was up-regulated in both nerve segments. In vitro experiments confirmed that Kif22 knockdown inhibited proliferation and migration of Schwann cells by modulating the activity of the extracellular signal-regulated kinase signaling pathway. Collectively, our findings provide a comparative framework of gene modules that are co-expressed in injured proximal and distal sciatic nerve segments, and identify Kif22 as a potential therapeutic target for promoting peripheral nerve injury repair via Schwann cell proliferation and migration. All animal experiments were approved by the Institutional Animal Ethics Committee of Nantong University, China (approval No. S20210322-008) on March 22, 2021.

The complexities of PKCα signaling in cancer

Protein kinase C α (PKCα) is a ubiquitously expressed member of the PKC family of serine/threonine kinases with diverse functions in normal and neoplastic cells. Early studies identified anti-proliferative and differentiation-inducing functions for PKCα in some normal tissues (e.g., regenerating epithelia) and pro-proliferative effects in others (e.g., cells of the hematopoietic system, smooth muscle cells). Additional well documented roles of PKCα signaling in normal cells include regulation of the cytoskeleton, cell adhesion, and cell migration, and PKCα can function as a survival factor in many contexts. While a majority of tumors lose expression of PKCα, others display aberrant overexpression of the enzyme. Cancer-related mutations in PKCα are uncommon, but rare examples of driver mutations have been detected in certain cancer types (e. g., choroid gliomas). Here we review the role of PKCα in various cancers, describe mechanisms by which PKCα affects cancer-related cell functions, and discuss how the diverse functions of PKCα contribute to tumor suppressive and tumor promoting activities of the enzyme. We end the discussion by addressing mutations and expression of PKCα in tumors and the clinical relevance of these findings.

SPP1 promotes Schwann cell proliferation and survival through PKCα by binding with CD44 and αvβ3 after peripheral nerve injury

BACKGROUND

Schwann cells (SCs) play a crucial role in Wallerian degeneration after peripheral nerve injury. The expression of genes in SCs undergo a series of changes, which greatly affect the proliferation and apoptosis of SCs as well as the fate of peripheral nerve regeneration. However, how do these genes regulate the proliferation and apoptosis of SCs remains unclear.

RESULTS

SPP1 and PKCα were found upregulated after human median peripheral nerve injury, which promoted SCs proliferation and survival. The promoted proliferation and inhibited apoptosis by SPP1 were blocked after the treatment of PKCα antagonist Gö6976. Whereas, the inhibited proliferation and enhanced apoptosis induced by silence of SPP1 could be rescued by the activation of PKCα, which suggested that SPP1 functioned through PKCα. Moreover, both CD44 and αvβ3 were found expressed in SCs and increased after peripheral nerve injury. Silence of CD44 or β3 alleviated the increased proliferation and inhibited apoptosis induced by recombinant osteopontin, suggesting the function of SPP1 on SCs were dependent on CD44 and β3.

CONCLUSION

These results suggested that SPP1 promoted proliferation and inhibited apoptosis of SCs through PKCα signaling pathway by binding with CD44 and αvβ3. This study provides a potential therapeutic target for improving peripheral nerve recovery.