Group B streptococcus exploits lipid rafts and phosphoinositide 3-kinase/Akt signaling pathway to invade human endometrial cells

Objective: We sought to determine the role lipid rafts and phosphoinositide 3-kinase (PI3K) in invasiveness of group B streptococci (GBS) to endometrial cells. Study Design: Antibiotic protection assay and electron microscopy were used to evaluate the invasion of GBS to human endometrial Ishikawa cells cholesterol-depleted by using methyl-beta-cyclodextrin or treated with PI3K inhibitors: wortmannin or LY294002. Immunoblotting analysis of Akt phosphorylation and cellular imaging of GFP-Akt-PH probe were used to assess PI3Ks activation in infected cells. Results: Infected Ishikawa cells streptococci are associated to membrane ruffles with morphological features of undergoing internalization. GBS remained attached but completely failed to invade to cholesterol-depleted human endometrial cells or displayed decreased invasiveness in the presence of PI3K inhibitors. Cholesterol depletion resulted in loss of membrane ruffling and dispersion of raft-associated molecules: monosialoganglioside GM1 and PI3K. Conclusion: This work provides the evidence that lipid rafts and raft-associated PI3K are implicated in GBS invasion to human endometrial cells.