Integrin expression, enterocyte maturation, and bacterial internalization

Area of Science:

• Microbiology
• Cell Biology
• Gastroenterology

Background:

• Mechanisms of enteric bacteria translocation are poorly understood.
• Adhesion molecules link enteric pathogens to host cells, but not typically normal enteric bacteria to enterocytes.
• Enteric pathogen studies suggest links between adhesion molecules, bacterial internalization, and enterocyte differentiation.

Purpose of the Study:

• Investigate integrin expression and differentiation in enterocytes.
• Determine enterocyte internalization of Salmonella typhimurium, Proteus mirabilis, and Escherichia coli.

Main Methods:

• Quantified integrin subunit expression (alpha2, alpha3, beta1) on Caco-2 and HT-29 enterocytes using ELISA.
• Observed bacteria-enterocyte interactions via light and scanning electron microscopy.
• Measured bacterial internalization using the gentamicin protection assay.

Main Results:

• Immature Caco-2 enterocytes showed increased alpha2, alpha3, and beta1 integrin subunit expression compared to mature cells.
• Immature HT-29 enterocytes had similar alpha3 and beta1 but decreased alpha2 expression versus mature cells.
• Bacterial internalization increased in immature enterocytes and in mature enterocytes with exposed lateral membranes, but not significantly different between immature and exposed mature enterocytes.

Conclusions:

• Integrin expression and enterocyte differentiation do not appear to drive bacterial internalization.
• Exposure of the lateral enterocyte membrane is a significant factor facilitating bacterial entry into enterocytes.