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Fusion of cytotrophoblasts with the overlying syncytiotrophoblast is an integral step in differentiation of the human placental villous trophoblast. Multiple factors, such as growth factors, hormones, cytokines, protein kinases, transcription factors and structural membrane proteins, were described to modulate trophoblast fusion. However, the knowledge on remodelling of the membrane-associated cytoskeleton during trophoblast fusion is very limited. This study describes the link between remodelling of spectrin-like α-fodrin and intercellular trophoblast fusion. Experiments with primary trophoblasts isolated from term placentas and the choriocarcinoma cell line BeWo revealed a biphasic strategy of the cells to achieve reorganization of α-fodrin. Syncytialization of trophoblasts was accompanied by down-regulation of α-fodrin mRNA, whereas the full-length α-fodrin protein was cleaved into 120 and 150 kDa fragments. Application of calpeptin and calpain inhibitor III did not affect α-fodrin fragmentation in primary term trophoblasts and forskolin-treated BeWo cells, but decreased secretion of β human chorionic gonadotropin. In contrast, inhibitors of caspases 3, 8 and 9 attenuated generation of the 120 kDa fragment and a general caspase inhibitor completely blocked fragmentation, suggesting an exclusive function of caspases in α-fodrin remodelling. Immunofluorescence double staining of human placenta revealed co-localization of active caspase 8 with α-fodrin positive vesicles in fusing villous cytotrophoblasts. These results suggest that caspase-dependent fragmentation of α-fodrin may be important for reorganization of the sub-membranous cytoskeleton during trophoblast fusion. [ABSTRACT FROM AUTHOR]