Dual pH/Activity Probes Expand the Cathepsin Toolkit

Area of Science:

• Biochemistry and Molecular Biology
• Cell Biology
• Microbiology

Background:

• Cathepsins are enzymes involved in cellular processes, and their activity is often pH-dependent.
• Organelle pH is crucial for cellular function and can be altered during infection.
• Salmonella typhimurium is an intracellular pathogen that manipulates host cell processes.

Purpose of the Study:

• To develop novel bifunctional probes capable of simultaneously monitoring cathepsin activity and pH.
• To investigate the dynamic changes in organelle pH induced by Salmonella typhimurium infection.
• To examine the impact of infection on both infected and bystander cells.

Main Methods:

• Design and synthesis of novel activity-based probes.
• Utilizing bifunctional probes to detect cathepsin activity and pH.
• Confocal microscopy and biochemical assays to analyze organelle pH and cathepsin activity in infected cells.

Main Results:

• The developed probes successfully reported both cathepsin activity and pH simultaneously.
• Salmonella typhimurium infection led to significant and dynamic alterations in the pH of cathepsin-containing organelles.
• These pH changes were observed in both directly infected cells and neighboring bystander cells.

Conclusions:

• Novel bifunctional probes provide a powerful tool for studying enzyme activity and microenvironment pH.
• Salmonella typhimurium actively modulates host cell organelle pH during infection.
• Infection effects on organelle pH extend beyond directly infected cells, impacting bystander cells.