# A Modified Tridecapeptide Probe for Imaging Cell Junction

## TL;DR

Researchers developed a fluorescent tridecapeptide to label cell junctions, successfully binding to ZO-1 in fixed cells but needing improved affinity for live cells.

## Contribution

A novel modified tridecapeptide was designed to label cell junctions, demonstrating binding to ZO-1 and feasibility of peptide-based imaging.

## Key findings

- The modified tridecapeptide binds to ZO-1 as confirmed by pulldown and immunoprecipitation assays.
- The peptide successfully labeled cell junctions in fixed Caco-2 cells but not in live cells due to low affinity.
- Peptide-based labeling of cell junctions is feasible but requires improved affinity for real-time applications.

## Abstract

Cell junctions, which are typically associated with dynamic cytoskeletons, are essential for a wide range of cellular activities, including cell migration, cell communication, barrier function and signal transduction. Observing cell junctions in real-time can help us understand the mechanisms by which they regulate these cellular activities. This study examined the binding capacity of a modified tridecapeptide from Connexin 43 (Cx43) to the cell junction protein zonula occludens-1 (ZO-1). The goal was to create a fluorescent peptide that can label cell junctions. A cell-penetrating peptide was linked to the modified tridecapeptide. The heterotrimeric peptide molecule was then synthesized. The binding of the modified tridecapeptide was tested using pulldown and immunoprecipitation assays. The ability of the peptide to label cell junctions was assessed by adding it to fixed or live Caco-2 cells. The testing assays revealed that the Cx43-derived peptide can bind to ZO-1. Additionally, the peptide was able to label cell junctions of fixed cells, although no obvious cell junction labeling was observed clearly in live cells, probably due to the inadequate affinity. These findings suggest that labeling cell junctions using a peptide-based strategy is feasible. Further efforts to improve its affinity are warranted in the future.