Date of Completion

6-23-2014

Embargo Period

6-23-2014

Major Advisor

Michael A. Lynes

Associate Advisor

Joerg Graf

Associate Advisor

Lawrence Silbart

Field of Study

Molecular and Cell Biology

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Small, cysteine-rich proteins called metallothioneins (MTs) bind essential divalent heavy metal cations, such as zinc and copper, as well as toxic heavy metals, such as cadmium and mercury. Stressful conditions such as exposure to heavy metals or reactive oxygen species (ROS) increase the expression of MTs. The numerous cysteine residues in MTs allow the protein to neutralize toxic effects of ROS, bind heavy metals, influence immune cell movement and proliferation. The bacteria Pseudomonas aeruginosa expresses an MT, PmtA, that is similar in structure the eukaryotic MTs. Evidence presented in these suggests that PmtA is an immunomodulatory protein, similar to the eukaryotic counterpart. Jurkat T cells pre-incubated with PmtA and subsequently exposed to a gradient of SDF-1a, lost the ability to move in a persistent direction, while Jurkat T cells pre-incubated with GST did respond to the SDF-1a gradient. Incubation with PmtA also decreased SDF-1a-induced internalization of the receptor CXCR4 on Jurkat T cells. P. aeruginosa strain PW4670 lacks PmtA expression, and is also more sensitive to oxidant exposure than the parent strain PA01. PW4670 also fails to produce pyocyanin, a secondary metabolite that produces ROS that can disrupts the immune response to P. aeruginosa. Due to the lack of pyocyanin by PW4670, PAO1 supernatant is more likely to kill macrophage cells in vitro and Galleria mellonella larvae in vivo, that PW4670 supernatant. Taken together, these results suggest that the expression of PmtA influences the virulence of P. aeruginosa, and may be a novel target for therapeutic intervention.

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