Abstract
Mutations that result in defective beta1-integrin focal adhesion formation were analyzed for effects on bacterial internalization. Mutations in the cytoplasmic domain of the beta1 chain that disrupt the sequence NPIY resulted in integrins deficient in bacterial uptake. Other mutations in the beta1 chain that reduced cytoskeletal association showed enhanced bacterial uptake. Replacement of the NPIY sequence of the beta1 subunit by the endocytosis internalization sequence PPGY resulted in integrin receptors highly proficient in bacterial internalization, yet severely defective in focal contact localization. Electron microscopy indicated that coated structures associated specifically with bacteria-binding beta1-integrins, with an apparent recruitment of coated pits from ventral cell surfaces to apical surfaces corresponding to nascent bacterial phagosomes. Clathrin inhibition studies indicated a role for the adaptor molecule AP2 as well as clathrin in integrin-mediated bacterial internalization. These results indicate that association of beta1-integrins with the cytoskeleton at focal contacts interferes with integrin-mediated bacterial internalization. Also, although actin polymerization is required for bacterial uptake, clathrin is probably involved in bacterial uptake promoted by beta-1-integrins.
Highlights
Integrins are heterodimeric receptors involved in numerous cellular processes including migration, differentiation, and adhesion to extracellular matrix and cell-surface proteins [1,2,3]
Human HEp-2 cells transfected with mutant derivatives of the chicken 1 chain were challenged with S. aureus coated with the chicken-specific anti-integrin 1 chain mAb CSAT
The chicken 1/human hybrids could be used to analyze the effect on bacterial uptake of mutations located in the cytoplasmic domain of the integrin 1 chain
Summary
Integrins are heterodimeric receptors involved in numerous cellular processes including migration, differentiation, and adhesion to extracellular matrix and cell-surface proteins [1,2,3]. The uptake of the enteroinvasive bacterium Yersinia pseudotuberculosis by 1-integrins has been studied in detail Uptake of this microorganism occurs via the bacterial surface protein invasin [20], which binds multiple 1-integrins [18]. Invasin-mediated bacterial uptake is accompanied by a local rearrangement of the actin network [21] and is inhibited by drugs that antagonize actin polymerization [22]. This has led to speculation that direct association of integrins with the cytoskeleton is required during internalization. We identify a region of the 1 subunit cytoplasmic domain that is critical for internalization and show a potentially antagonistic relationship between cytoskeletal association of the cytoplasmic domain and bacterial uptake
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
