A PAL for Schistosoma mansoni PHM

Area of Science:

• Parasitology
• Molecular Biology
• Drug Discovery

Background:

• Parasitic helminth neuromuscular function is a target for chemotherapy.
• Neuropeptide signaling is vital for helminth motor function but lacks anthelmintic targets.
• Most bioactive neuropeptides have a C-terminal amide (NH(2)) motif, formed by peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidylglycine alpha-amidating lyase (PAL).

Purpose of the Study:

• To describe the cDNA encoding Schistosoma mansoni PAL (SmPAL).
• To investigate the function and characteristics of SmPAL.
• To assess SmPAL as a potential drug target for schistosomiasis.

Main Methods:

• Described SmPAL cDNA and heterologously expressed the enzyme.
• Compared SmPAL's catalytic activity and optimal pH to other PALs.
• Used in situ hybridization to determine SmPAL mRNA expression patterns.
• Applied RNA interference (RNAi) to knockdown Sm-pal-1 transcript in larval schistosomula.

Main Results:

• Described a monofunctional SmPAL enzyme with functionally similar catalytic activity and optimal pH to other PALs, but with key amino acid substitutions.
• Demonstrated SmPAL mRNA expression in the neuronal cell bodies of adult schistosomes' central nervous system.
• Observed variable and inconsistent RNAi-mediated knockdown of Sm-pal-1 transcript without discernible aberrant phenotypes.

Conclusions:

• Schistosome amidating enzymes like SmPAL are appealing drug targets due to their role in neuropeptide maturation.
• Validation of SmPAL as a drug target is hindered by inconsistent RNAi outcomes in schistosomes, possibly due to tissue-specific differences or neuronal target refractoriness.
• Development of more robust reverse genetic tools is necessary for efficient neuronal gene function studies and drug target validation in schistosomes.