A PTP1B-Cdk3 Signaling Axis Promotes Cell Cycle Progression of Human Glioblastoma Cells through an Rb-E2F Dependent
Olga Villamar-Cruz1,2, Marco Antonio Loza-Mejía3, Alonso Vivar-Sierra3
1Unidad de Investigación en Biomedicina (UBIMED), Facultad de Estudios Superiores-Iztacala, UNAM Tlalnepantla, Estado de México, Mexico.
Abstract:
PTP1B plays a key role in developing different types of cancer. However, the molecular mechanism underlying this effect is unclear. To identify molecular targets of PTP1B that mediate its role in tumorigenesis, we undertook a SILAC-based phosphoproteomic approach, which allowed us to identify Cdk3 as a novel PTP1B substrate. Substrate trapping experiments and docking studies revealed stable interactions between the PTP1B catalytic domain and Cdk3. In addition, we observed that PTP1B dephosphorylates Cdk3 at tyrosine residue 15 in vitro and interacts with it in human glioblastoma cells. Next, we found that pharmacological inhibition of PTP1B or its depletion with siRNA leads to cell cycle arrest with diminished activity of Cdk3, hypophosphorylation of Rb, and the downregulation of E2F target genes Cdk1, Cyclin A, and Cyclin E1. Finally, we observed that the expression of a constitutively active Cdk3 mutant bypasses the requirement of PTP1B for cell cycle progression and expression of E2F target genes. These data delineate a novel signaling pathway from PTP1B to Cdk3 required for efficient cell cycle progression in an Rb-E2F dependent manner in human GB cells.
Insights
Protein tyrosine phosphatase 1B (PTP1B) targets Cyclin-dependent kinase 3 (Cdk3) to drive cancer cell cycle progression. Inhibiting PTP1B halts cell division by deactivating Cdk3, offering a potential therapeutic strategy.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Protein tyrosine phosphatase 1B (PTP1B) is implicated in cancer development, but its precise molecular targets and mechanisms remain largely unknown.
- Understanding PTP1B's role in tumorigenesis requires identifying its direct substrates and downstream signaling pathways.
Purpose of the Study:
- To identify novel molecular targets of PTP1B involved in cancer progression.
- To elucidate the functional relationship between PTP1B and its identified targets in human glioblastoma cells.
Main Methods:
- Utilized SILAC-based phosphoproteomics to discover PTP1B substrates.
- Performed substrate trapping, docking studies, in vitro dephosphorylation assays, and siRNA-mediated depletion.
- Investigated cell cycle progression, protein activity, and gene expression in response to PTP1B modulation and Cdk3 activity.
Main Results:
- Identified Cyclin-dependent kinase 3 (Cdk3) as a novel substrate of PTP1B, with direct interaction and dephosphorylation at tyrosine 15.
- Pharmacological inhibition or genetic depletion of PTP1B caused cell cycle arrest, reduced Cdk3 activity, hypophosphorylation of Retinoblastoma protein (Rb), and downregulation of E2F target genes.
- Expression of a constitutively active Cdk3 mutant rescued cell cycle progression and gene expression, bypassing the need for PTP1B.
Conclusions:
- Established a novel signaling pathway where PTP1B dephosphorylates and activates Cdk3.
- This PTP1B-Cdk3 axis is crucial for Rb-E2F-mediated cell cycle progression in human glioblastoma.
- Targeting PTP1B may represent a viable strategy for inhibiting glioblastoma proliferation.
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