Interrogating Endogenous Protein Phosphatase Activity with Rationally Designed Chemosensors

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Protein phosphatases are crucial regulators of cellular signaling pathways.
• Dysregulation of protein phosphatase activity is implicated in various human diseases, including metabolic disorders and cancer.
• Existing methods for measuring phosphatase activity often lack specificity or sensitivity for endogenous enzymes in complex biological samples.

Purpose of the Study:

• To develop a versatile and sensitive method for repurposing protein kinase chemosensors to determine endogenous protein phosphatase activity.
• To design and validate a specific chemosensor for protein tyrosine phosphatase-1B (PTP1B), a key signaling node in human diseases.
• To apply this novel assay for temporal analysis of PTP1B activity and its role in disease models.

Main Methods:

• Repurposing of Sox (sulfonamido-oxine) fluorophore-based chemosensors for protein phosphatase activity detection.
• Design and optimization of a direct chemosensor for PTP1B.
• Characterization of sensor sensitivity and selectivity against homologous phosphatases.
• Application of the chemosensor assay in cell lysates (HepG2 cells stimulated with insulin) and tissue homogenates (rat model of nonalcoholic fatty liver disease).

Main Results:

• The developed PTP1B chemosensor exhibits high sensitivity, detecting as little as 6 pM of recombinant PTP1B.
• The sensor demonstrates remarkable selectivity for PTP1B over closely related tyrosine phosphatases.
• The assay successfully monitored temporal changes in endogenous PTP1B activity in response to insulin stimulation in HepG2 cells.
• Elevated PTP1B catalytic activity was directly observed in a rat model of nonalcoholic fatty liver disease (NAFLD).

Conclusions:

• This versatile approach enables specific determination of endogenous protein phosphatase activity in complex biological matrices.
• The PTP1B-specific chemosensor provides a sensitive and selective tool for studying PTP1B function in cellular signaling and disease.
• The assay platform offers broad utility for monitoring phosphatase activity dynamics in human diseases, facilitating biomarker discovery and therapeutic development.