Investigating the structure and function of PEPITEM, a novel inhibitor of T cell transmigration

Apta, Bonita Harriet Radha (2016). Investigating the structure and function of PEPITEM, a novel inhibitor of T cell transmigration. University of Birmingham. Ph.D.

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Abstract

Peptide inhibitor of trans-endothelial migration (PEPITEM) is a B cell-secreted peptide which inhibits T cell trafficking across cytokine-stimulated endothelium. This homeostatic mechanism is lost in autoimmune and chronic inflammatory diseases, leading to inappropriate T cell trafficking with pathological consequences, e.g. in type-1 diabetes and rheumatoid arthritis. We aimed to investigate the structure and function of PEPITEM in vitro and in vivo to establish its pharmacokinetics, therapeutic potential, and underlying molecular mechanisms.

The efficacy of PEPITEM was verified, showing the same regulatory control of T cell trafficking as previously reported. Nuclear magnetic resonance (NMR) studies revealed PEPITEM to be a linear peptide lacking secondary structure. Intravenous administration of radiolabelled native PEPTEIM in wild-type mice showed rapid clearance by the renal circulation, conferring a circulatory half-life of <2 minutes. Common conjugation strategies employed to modify PEPITEM, e.g. PEGylation, did not affect peptide function, demonstrating its potential for therapeutic development. The evolution of PEPITEM from its parent protein, 14-3-3ζ was investigated. PEPITEM is probably cleaved from 14-3-3ζ by matrix metalloproteinase 9 extracellularly after exocytosis from B cells. Interestingly, this generates a 17aa peptide which requires additional proteolytic processing to evolve a smaller biologically active pharmacophore.

These observations add to our current knowledge of the PEPITEM paradigm, which appears central to regulated trafficking of T cells. Future work will formulate new PEPITEM versions with suitable pharmacological profiles, and screen them for function in vitro and in vivo to develop suitable therapeutic agents.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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