Cholangiocyte myosin IIB is required for localized aggregation of sodium glucose cotransporter 1 to sites of Cryptosporidium parvum cellular invasion and facilitates parasite internalization.

Publication Type:

Journal Article


Infection and immunity, Volume 78, Issue 7, p.2927-36 (2010)


Aquaporin 1digestive disease, digestive deseases Bile Ductsdigestive disease, digestive deseases Blotting, Westerndigestive disease, digestive deseases Cell Linedigestive disease, digestive deseases Cryptosporidiosisdigestive disease, digestive deseases Cryptosporidium parvumdigestive disease, digestive deseases Fluorescent Antibody Techniquedigestive disease, digestive deseases Heterocyclic Compounds with 4 or More Ringsdigestive disease, digestive deseases Host-Parasite Interactionsdigestive disease, digestive deseases Humansdigestive disease, digestive deseases Microscopy, Electron, Scanningdigestive disease, digestive deseases Nonmuscle Myosin Type IIAdigestive disease, digestive deseases Nonmuscle Myosin Type IIBdigestive disease, digestive deseases Reverse Transcriptase Polymerase Chain Reactiondigestive disease, digestive deseases Sodium-Glucose Transporter 1


Internalization of the obligate intracellular apicomplexan parasite, Cryptosporidium parvum, results in the formation of a unique intramembranous yet extracytoplasmic niche on the apical surfaces of host epithelial cells, a process that depends on host cell membrane extension. We previously demonstrated that efficient C. parvum invasion of biliary epithelial cells (cholangiocytes) requires host cell actin polymerization and localized membrane translocation/insertion of Na(+)/glucose cotransporter 1 (SGLT1) and of aquaporin 1 (Aqp1), a water channel, at the attachment site. The resultant localized water influx facilitates parasite cellular invasion by promoting host-cell membrane protrusion. However, the molecular mechanisms by which C. parvum induces membrane translocation/insertion of SGLT1/Aqp1 are obscure. We report here that cultured human cholangiocytes express several nonmuscle myosins, including myosins IIA and IIB. Moreover, C. parvum infection of cultured cholangiocytes results in the localized selective aggregation of myosin IIB but not myosin IIA at the region of parasite attachment, as assessed by dual-label immunofluorescence confocal microscopy. Concordantly, treatment of cells with the myosin light chain kinase inhibitor ML-7 or the myosin II-specific inhibitor blebbistatin or selective RNA-mediated repression of myosin IIB significantly inhibits (P < 0.05) C. parvum cellular invasion (by 60 to 80%). Furthermore ML-7 and blebbistatin significantly decrease (P < 0.02) C. parvum-induced accumulation of SGLT1 at infection sites (by approximately 80%). Thus, localized actomyosin-dependent membrane translocation of transporters/channels initiated by C. parvum is essential for membrane extension and parasite internalization, a phenomenon that may also be relevant to the mechanisms of cell membrane protrusion in general.