Septins are guanosine-5'-triphosphate-binding
proteins involved in wide-ranging cellular processes including cytokinesis, vesicle trafficking, membrane remodelling and scaffolds, and with diverse binding partners. Precise roles for these structural
proteins in most processes often remain elusive. Identification of small molecules that inhibit
septins could aid in elucidating the functions of
septins and has become increasingly important, including the description of roles for
septins in pathogenic phenomena such as
tumorigenesis. The
plant growth regulator forchlorfenuron, a synthetic
cytokinin known to inhibit
septin dynamics, likely represents an informative probe for
septin function. This report deals with
septins of the human blood fluke Schistosoma mansoni and their interactions with
forchlorfenuron. Recombinant forms of three schistosome
septins, SmSEPT5, SmSEPT7.2 and SmSEPT10, interacted with
forchlorfenuron, leading to rapid polymerization of filaments. Culturing developmental stages (miracidia, cercariae, adult males) of schistosomes in FCF at 50-500 μM rapidly led to
paralysis, which was reversible upon removal of the
cytokinin. The reversible
paralysis was concentration-, time- and developmental stage-dependent. Effects of
forchlorfenuron on the cultured schistosomes were monitored by video and/or by an xCELLigence-based assay of motility, which quantified the effect of
forchlorfenuron on fluke motility. The findings implicated a mechanism targeting a molecular system controlling movement in these developmental stages: a direct effect on muscle contraction due to
septin stabilization might be responsible for the reversible
paralysis, since enrichment of
septins has been described within the muscles of schistosomes. This study revealed the reversible effect of
forchlorfenuron on both schistosome motility and its striking impact in hastening polymerization of
septins. These novel findings suggested routes to elucidate roles for
septins in this pathogen, and exploitation of derivatives of
forchlorfenuron for anti-schistosomal drugs.