Base-Exchange Enabling the Visualization of SARM1 Activities in Sciatic Nerve-Injured Mice

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Enzyme activity is crucial for maintaining homeostasis in living organisms.
• Aberrant enzyme activity is linked to various human diseases, necessitating in vivo activity detection for pathological studies.

Purpose of the Study:

• To design and synthesize novel small-molecule-activatable fluorescent probes for imaging Sterile Alpha and TIR Motif-containing 1 (SARM1) activity.
• To develop a sensitive tool for monitoring SARM1's transglycosidase activity.

Main Methods:

• Synthesis of small-molecule-activatable fluorescent probes.
• Characterization of probe 1a's reactivity with NAD+ in the presence of SARM1, CD38, and NADase.
• Assessment of fluorescence enhancement, Stokes shift, and red shift upon reaction.
• Evaluation of probe 1a in live-cell imaging and in vivo models.

Main Results:

• Probe 1a selectively reacted with NAD+ via SARM1's transglycosidase activity, forming a highly emissive product AD-1a.
• The probe exhibited a ~100-fold fluorescence enhancement within 20 minutes, with a 150 nm Stokes shift and 100 nm red shift.
• Probe 1a demonstrated superior reactivity and sensitivity compared to existing SARM1 imaging probes.
• Successful application of probe 1a in live-cell imaging and in vivo detection of SARM1 activity in a mouse model of sciatic nerve injury.

Conclusions:

• A novel, highly sensitive fluorescent probe (1a) was developed for SARM1 activity imaging.
• The probe's selectivity and performance surpass current methods, offering new possibilities for SARM1 research.
• This tool has potential applications in studying diseases associated with SARM1 and in neurological injury models.