Regenerative potential of von Hippel-Lindau tumor suppressor protein

Abstract

The von Hippel-Lindau (VHL) protein, traditionally known for oxygen sensing via HIF-1α degradation, is now recognized as a multifunctional regulator of neural stem cell (NSC) fate and central nervous system regeneration. This review examines VHL’s role in lineage specification and its therapeutic potential. Under normoxia, VHL promotes rapid neuronal differentiation by suppressing JAK2/STAT and Notch signaling pathways. This relief of repression activates proneural bHLH factors like Neurogenin2 and Ascl1, leading to the generation of electrophysiologically mature, MAP2-positive neurons. Conversely, hypoxia-induced HIF-1α stabilization biases NSCs toward a glial fate, supporting survival and astrocytic differentiation in the injured environment. Beyond its canonical role, specialized modules expand VHL’s utility: The transferable BC-box motif can independently induce neuronal commitment in various somatic stem cells, while the Daam²-VHL-Nedd4 axis supports oligodendrocyte maturation and remyelination. Translational studies in models of Parkinson’s disease and spinal cord injury demonstrate that VHL-based strategies can achieve significant functional recovery. Understanding the context-dependent dynamics of VHL signaling is crucial for advancing regenerative therapies for neurodegenerative and demyelinating disorders.

Key Words: Regeneration; Von Hippel-Lindau; Mesenchymal stem cell; Neuronal disease; Hypoxia-inducible factor

Core Tip: The mechanism of action of von Hippel-Lindau (VHL) involved in neuronal differentiation is mediated through the inhibition of downstream signaling pathways, JAK-STAT, and HIF-VEGF pathways. In addition, because VHL promotes nerve regeneration, it is expected to be applied in neuronal regenerative medicine for traumatic brain injury and stroke.

INTRODUCTION

The von Hippel-Lindau (VHL) tumor suppressor protein is well-established as a central gatekeeper of the cellular oxygen-sensing pathway. Functioning as the substrate-recognition component of the VBC-Cul2 E3 ubiquitin ligase complex, VHL targets HIF-1α for proteasomal degradation under normoxic conditions[1,2]. While its role in tumor suppression and oxygen homeostasis has dominated scientific literature for decades, emerging evidence suggests that VHL’s functional repertoire extends far beyond these canonical processes. Recent studies have identified VHL as a critical regulator of neural development, stem cell fate specification, and regenerative processes within the central nervous system (CNS). Research has demonstrated that forced expression of VHL in neural stem cells (NSCs) triggers rapid differentiation into electrophysiologically mature neurons, characterized by significant peak inward currents. This pro-neuronal effect is achieved through the coordinated suppression of inhibitory signaling pathways, such as JAK/STAT and Notch, which relieves the repression of key proneural bHLH factors. Furthermore, the discovery of the transferable BC-box motif within VHL and the Daam²-VHL-Nedd4 axis has expanded the therapeutic potential of VHL-based strategies to include both neuronal induction in various somatic stem cells and oligodendrocyte remyelination[3,4]. Given the significant challenges in treating neurodegenerative diseases and CNS injuries, understanding the multifunctional nature of VHL is paramount. This review aims to synthesize current knowledge regarding VHL’s role in neural lineage commitment, explore the molecular mechanisms underlying its regenerative potential, and discuss the translational implications of modulating VHL activity for clinical applications in regenerative medicine[5] (Figure 1).

Figure 1 Regenerative potential and molecular mechanisms of the von Hippel-Lindau protein in neural and somatic stem cells. Normoxia (Left): Under normal oxygen conditions, von Hippel-Lindau (VHL) functions as the substrate-recognition component of the VHL-Elongin B/C-Cullin2-RBX1 E3 ubiquitin ligase complex. This complex targets several key signaling molecules for proteasomal degradation, including JAK2/STAT, NOTCH (HES1/5), SMAD, and HIF-1α. The suppression of these pathways leads to the “relief of repression” for proneural bHLH factors (e.g., NEUROGENIN2, ASCL1/MASH1), thereby promoting the differentiation of neural stem cells (NSCs) into functional, mature neurons (MAP2+) characterized by robust electrophysiological activity (> 4000 pA). Hypoxia (right): Under low oxygen conditions, VHL-mediated degradation is inhibited, leading to HIF1α stabilization. Stabilized HIF-1α translocates to the nucleus and activates target genes such as SOX9, VEGF, and EPO. This pathway shifts the NSC differentiation bias toward the glial lineage, specifically promoting the formation of GFAP+ astrocytes. Specialized regenerative modules (bottom center): Transferable BC-Box motif: A synthetic BC-box peptide can mimic VHL function to induce neuronal differentiation in various somatic stem cells (e.g., bone marrow, adipose, and skin-derived cells), suggesting a modular application for regenerative medicine. Oligodendrocyte axis: The Daam²-NEDD4 axis regulates VHL via non-degradative ubiquitination. VHL stabilization through this pathway is critical for remyelination, facilitating the maturation of oligodendrocytes and the repair of myelin sheaths. VHL: Von Hippel-Lindau; NSCs: Neural stem cells.

REGENERATIVE POTENTIAL OF VHL TUMOR SUPPRESSOR PROTEIN

These findings have broadened the conceptual framework surrounding VHL, positioning it not only as a tumor suppressor but also as a potent regulator of neural lineage commitment and CNS repair. VHL participates in multiple signaling pathways that influence NSC fate, including JAK/STAT, Notch, Smad, and HIF-dependent cascades[6,7]. In addition, the BC-box motif within VHL-a short peptide sequence responsible for binding Elongin B/C-has emerged as a transferable module capable of inducing neuronal differentiation in diverse somatic stem cell types[8]. More recently, the discovery of the Daam²-VHL-Nedd4 axis has expanded the functional repertoire of VHL to include oligodendrocyte development and remyelination[9]. Together, these findings suggest that VHL is a multifunctional regulator whose activity is highly context-dependent and dynamically shaped by environmental cues such as oxygen tension. VHL functions as the substrate-recognition module of the VBC-Cul2 E3 ubiquitin ligase complex, which includes Elongin B, Elongin C, Cullin-2, and Rbx1[9]. The best-characterized substrate of this complex is HIF-1α, which is hydroxylated under normoxic conditions and subsequently recognized by VHL. However, VHL also regulates additional substrates relevant to neural differentiation, including JAK2 and components of the Notch signaling pathway[10]. The BC-box motif within VHL mediates binding to Elongin B/C and is essential for assembly of the VBC-Cul2 complex. Synthetic peptides containing this motif can enter cells and recapitulate VHL’s differentiation-inducing effects, suggesting that BC-box-mediated recruitment of Elongin B/C may redirect ubiquitination toward substrates that suppress glial fate or promote neuronal commitment[3]. The ability of the BC-box motif to function independently of the full VHL protein raises important mechanistic questions. One possibility is that BC-box–mediated recruitment of Elongin B/C alters the balance of ubiquitination within the cell, selectively degrading inhibitors of neuronal differentiation. Another possibility is that the BC-box motif interacts with cofactors shared by VHL and SOCS family proteins, which also contain BC-box motifs and exhibit similar neuronal induction activity[3]. This raises the possibility of a conserved mechanism of lineage control mediated by BC-box–dependent ubiquitin ligase complexes.

Under normoxic conditions, VHL promotes neuronal differentiation through coordinated suppression of JAK2/STAT, Smad, and Notch signaling pathways. VHL-mediated degradation of JAK2 reduces downstream STAT activation, which in turn diminishes transcription of glial-promoting genes[5]. This mechanism aligns with findings in Drosophila and mammalian systems showing that JAK/STAT signaling maintains progenitor states and inhibits neuronal differentiation[11]. Notch signaling is another major pathway suppressed by VHL. Notch activation induces expression of Hes1 and Hes5, transcriptional repressors that inhibit proneural bHLH factors such as Neurogenin2 and Mash1/Ascl1[12]. These proneural factors are essential for neuronal lineage commitment and activate downstream genes required for synaptic formation, axonal growth, and electrophysiological maturation[9]. By attenuating Notch-dependent Hes expression, VHL indirectly relieves repression of Neurogenin2 and Ascl1, thereby promoting neuronal differentiation[12]. The convergence of JAK2/STAT and Notch suppression provides a mechanistic explanation for the rapid and robust neuronal induction observed following VHL overexpression. In previous studies, VHL-introduced NSCs differentiated into MAP2-positive neurons within days, and electrophysiological analysis revealed peak inward currents exceeding 4000 pA-more than three times those of naturally differentiated neurons[3]. These findings suggest that VHL not only initiates neuronal differentiation but also accelerates maturation by enabling expression of bHLH-dependent genes involved in ion channel formation and synaptic function. Under hypoxic conditions, prolyl hydroxylation of HIF1α is impaired, preventing its recognition by VHL and leading to HIF1α stabilization[3,6]. Stabilized HIF-1α activates a transcriptional program that includes vascular endothelial growth factor (VEGF) and erythropoietin but also glial-promoting factors such as Sox9 and genes associated with astrocytic differentiation[13,14]. These downstream targets contribute to the observed shift of NSCs from MAP2-positive neuronal lineages to GFAP-positive glial lineages under hypoxia. Importantly, HIF-1α exerts both cell-autonomous and non-cell-autonomous effects. Within NSCs, HIF-1α promotes survival and glial differentiation[14]. In the vascular niche, HIF-dependent VEGF secretion enhances endothelial survival and angiogenesis, creating a microenvironment that favors glial lineage stabilization[14]. This dual mechanism explains why hypoxia promotes gliogenesis even when NSCs retain intrinsic neuronal potential. These findings also have implications for CNS injury. After traumatic brain injury or stroke, hypoxia stabilizes HIF1α, which supports NSC survival and migration to ischemic regions[15]. However, prolonged HIF1α activity may bias differentiation toward glial lineages, potentially limiting neuronal regeneration. Understanding the temporal dynamics of VHL-HIF signaling is therefore essential for designing regenerative therapies. The BC-box motif within VHL is a short peptide sequence that mediates binding to Elongin B/C and is essential for assembly of the VBC-Cul2 complex. Remarkably, synthetic peptides containing this motif are sufficient to induce neuronal differentiation in diverse somatic stem cell types, including skin-derived precursors, bone marrow stromal cells[3], adipose-derived stem cells, and human epidermal stem cells. This portability suggests that BC-box–mediated recruitment of Elongin B/C may redirect ubiquitination toward substrates that suppress glial fate or enhance neuronal commitment. SOCS family proteins contain homologous BC-box motifs and similarly promote neuronal differentiation, raising the possibility of shared substrates or cofactors[3]. The consistent neuronal bias induced by BC-box motifs across cell types highlights their potential as programmable modules for regenerative medicine. Previous studies demonstrated that intracellular delivery of synthetic BC-box peptides induces rapid neuronal differentiation and generates electrophysiologically mature neurons[3]. These findings suggest that BC-box–based therapies may offer a practical alternative to gene transfer approaches, potentially reducing risks associated with viral vectors and long-term overexpression of E3 ligases. Recent work has identified a novel pathway in which the E3 ligase Nedd4 stabilizes VHL during oligodendrocyte differentiation. Nedd4 appears to modify VHL through non-degradative ubiquitination, enhancing its stability and enabling efficient degradation of substrates that inhibit oligodendrocyte maturation[4]. This stabilization is essential for developmental myelination and for remyelination in multiple sclerosis models. Integrating this pathway with VHL’s neuronal functions suggests that VHL acts as a lineage-flexible regulator whose effects depend on cellular context and upstream modulators. Whereas BC-box–mediated VHL activity promotes neuronal differentiation in NSCs and somatic stem cells, Nedd4-stabilized VHL supports oligodendrocyte maturation in the postnatal CNS. The regenerative response to CNS injury unfolds across distinct temporal phases, and VHL plays different roles at each stage. Immediately after injury, hypoxia stabilizes HIF1α, which promotes NSC survival, migration, and vascular niche maintenance[16]. During this acute phase, high VHL activity could be counterproductive, as it would promote HIF1α degradation and potentially impair survival mechanisms. As oxygen tension begins to normalize during the subacute phase, HIF-dependent VEGF signaling supports angiogenesis and tissue repair, while NSCs migrate toward injured regions. During this period, VHL activity gradually reasserts control, reducing HIF-1α levels and preparing NSCs for differentiation. In the chronic phase, VHL-mediated degradation of HIF-1α promotes neuronal differentiation, while BC-box–dependent mechanisms enhance electrophysiological maturation and Nedd4-stabilized VHL supports oligodendrocyte maturation and remyelination[4]. Translational studies have demonstrated the therapeutic potential of VHL-based interventions. In Parkinson’s disease models, transplantation of VHL-introduced NSCs resulted in substantial dopaminergic differentiation, with more than 50% of transplanted cells differentiating into TH-positive neurons and 30% of animals exhibiting complete normalization of rotational behavior[5]. In spinal cord injury models, delivery of BC-box peptides to NSCs or bone marrow stromal cells enhanced neuronal differentiation and promoted functional recovery. In stroke and traumatic brain injury, HIF-1α plays a critical role in NSC survival and migration, and as the primary upstream regulator of HIF-1α, VHL is central to post-injury repair and neuroplasticity[16]. In demyelinating diseases such as multiple sclerosis, the Daam²-VHL-Nedd4 axis plays a vital role in oligodendrocyte development and remyelination, suggesting that enhancing VHL stability in oligodendrocyte progenitor cells may promote remyelination[11]. Despite these promising findings, several limitations remain. The molecular mechanisms linking VHL activity to regenerative outcomes are not fully understood, particularly the substrate specificity of BC-box–mediated ubiquitination. The potential off-target effects of VHL overexpression or BC-box peptide delivery also require further investigation. In addition, the temporal dynamics of VHL-HIF signaling during CNS injury must be carefully considered when designing therapeutic strategies. Future studies should aim to identify specific substrates targeted by VHL during neuronal and oligodendrocyte differentiation, elucidate the mechanisms underlying BC-box–mediated neuronal induction, and explore the therapeutic potential of modulating VHL activity in vivo.

CONCLUSION

In conclusion, VHL is a multifunctional regulator of neural differentiation and regeneration whose activity is highly context-dependent. Under normoxic conditions, VHL promotes neuronal differentiation through suppression of JAK2/STAT and Notch signaling and activation of proneural bHLH factors. Under hypoxic conditions, HIF-1α stabilization promotes glial differentiation and supports NSC survival and migration. The BC-box motif within VHL functions as a portable neuronal induction module, while the Daam²-VHL-Nedd4 axis supports oligodendrocyte maturation and remyelination. Together, these pathways position VHL as a promising target for regenerative therapies in neurodegenerative diseases, CNS injury, and demyelinating disorders.