Assessment of Schistosoma mansoni cAMP phosphodiesterases through complementation in a customised Trypanosoma brucei cell line

Aloraini, Maha Abdullah (2026) Assessment of Schistosoma mansoni cAMP phosphodiesterases through complementation in a customised Trypanosoma brucei cell line. PhD thesis, University of Glasgow.

Abstract

The Schistosoma mansoni phosphodiesterase (SmPDE) enzymes have emerged as antiparasite targets because of their role in parasitic biology via cyclic nucleotides and differences with their mammalian counterparts. Previous studies conducted in the lab of De Koning described a characterization of the SmPDE family and showed that the SmPDE4A was able to replace the essential Trypanosoma brucei PDEB1/B2 system. However, it is still not clear whether there were other SmPDE proteins incompatible with the same system or negative results resulted from an inadequate construction design. Therefore, the goal of the current study was to continue investigating the ability of other SmPDE proteins to complement the essential function and use them for drug profiling. Unfused full-length constructions of SmPDE7var, SmPDE1, SmPDE8, and SmPDE9C were made and inserted into the conditional knockout T. brucei cells deficient in PDEB1/B2 under tetracycline inducible control. Simultaneously, catalytic domain constructs were prepared by introducing the catalytic domains of SmPDE4A, SmPDE7var, and SmPDE11 into the TbrPDEB1 construction to assess whether the negative results were linked to the specific localization or regulation of the SmPDE protein. It turned out that full-length constructions of all four proteins were able to complement the essential system. On the contrary, only SmPDE4A and SmPDE7var and not SmPDE11 worked as replacements of the catalytic domain. Late addition of tetracycline led to cell death and not arrest in proliferation. Finally, sensitivity of the created complementation lines was estimated using the dose–response assay in the presence of various drugs and calculating EC50 by fitting a nonlinear regression curve, reporting the value with its standard error and 95% CI. Pentamidine proved the highest activity, and experimental compounds showed construct-dependent potency differences in both systems. Thus, the research expanded the existing knowledge of complementation analyses of SmPDE and allowed to establish the relative importance of the two factors discussed.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Schistosoma mansoni, phosphodiesterases, Trypanosoma brucei, functional complementation, catalytic-domain replacement, drug sensitivity profiling.
• Subjects: Q Science > QR Microbiology; Q Science > QR Microbiology > QR180 Immunology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Supervisor's Name: de Koning, Professor Harry
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-86195
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 Aug 2026 09:25
• Last Modified: 24 Aug 2026 09:25
• Thesis DOI: 10.5525/gla.thesis.86195
• URI: https://theses.gla.ac.uk/id/eprint/86195