Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Meningococcal PorA-Loop4 induces G1 cell cycle arrest through the Akt signaling pathway (#235)

Rininta Firdaus 1 2 , Neil J. Oldfield 1 , Karl G. Wooldridge 1
  1. School of Life Sciences, University of Nottingham, Nottingham, NOTTINGHAMSHIRE, United Kingdom
  2. Faculty of Pharmacy, Pancasila University, South Jakarta, DKI Jakarta, Indonesia

Neisseria meningitidis (meningococcus) is a major meningitis-causing bacteria and is known for its ability to breach the blood-brain barrier (BBB). Meningococcus binds to the Laminin receptor (LAMR) on the surface of the endothelium, which is part of the blood brain barrier [1]. The meningococcal surface proteins PorA and PilQ were previously identified as the bacterial ligands responsible for binding and, subsequently the LAMR-binding moiety of PorA was localised to its fourth extracellular loop (PorA-Loop4) [2]. Using a circularised peptide corresponding to PorA-Loop 4 from N. meningitidis MC58, the PorA-LAMR interaction induced specific cellular responses in human brain microvascular endothelial cells (HBMECs) including G1 cell cycle arrest. Flow cytometric analysis indicated that the treatment of HBMECs with PorA-Loop4 for 24 h caused a significant reduction of cells (20%) at S-phase and a corresponding increase (23%) in the G1 population. Immunoblotting and quantitative real time PCR (qRT-PCR) analysis suggested that a blockade in Akt signaling (key proteins including Akt, GSK-3β, CyclinD1, and CDK4) contributes to the G1 arrest. Immunoblotting showed that the expression of phosphorylated GSK-3β and CDK4 were significantly increased in treated HBMECs. In contrast, the expression of phosphorylated Akt and Cyclin D1 were decreased following treatment. Transcriptome analysis using qRT-PCR confirmed that treatment of HBMECs with PorA-Loop4 peptide for 2, 4, 8, or 24 h increased gene expression of CDK4, and decreased expression of Cyclin D1. These data suggest that PorA-Loop4 induced G1 arrest through the Akt signaling pathway via Akt/GSK-3β/CyclinD1/CDK4.

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