Year of Award

2009

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Other Degree Name/Area of Focus

Integrative Microbiology and Biochemistry, Molecular Biology

Department or School/College

Division of Biological Sciences

Committee Chair

Ralph C. Judd

Commitee Members

Harlan D. Caldwell, J. Stephen Lodmell, Mark L. Grimes, Diana I. Lurie

Abstract

C. trachomatis is an obligate intracellular pathogen that is a leading cause of sexually transmitted diseases and blinding trachoma worldwide. Genes encoded in the plasticity zone (PZ) and the polymorphic membrane proteins (Pmps) represent major virulence determinants for chlamydiae. Elucidating their roles will be essential for the development of a vaccine to control human chlamydial diseases.

The PZ MACPF domain protein CT153 is expressed as a 91 kDa polypeptide in elementary bodies of all human serovariants suggesting a common function. CT153 is processed during infection into an N-terminal p42 and a C-terminal p59 that contains the MACPF domain. Similar processing was observed following heterologous expression suggesting autocatalytic proteolysis. Immunoelectron microscopy revealed that CT153 shared localization patterns with Hsp60 and CT155, a PZ phospholipase D (PLD) paralog. CT153 stained reticulate bodies (RBs) adjacent to the inclusion membrane and morphologically atypical RBs that tended to associate with inclusion-sequestered lipid droplets. Collectively, these results suggest CT153 and the PZ PLDs share a concomitant function within a subpopulation of RBs involving lipid metabolism or acquisition.

PmpD is a vaccine candidate as it is highly conserved and is a target of cross-reactive neutralizing antibodies. Immunoaffinity-purified native PmpD exists as an oligomer with a 23 nm flower-like structure. Two-dimensional blue native/SDS-PAGE analyses showed oligomers were comprised of full length PmpD and two processed fragments: p73 passenger domain (PD) and p82 translocator domain. PmpD undergoes infection- dependent proteolysis late during the developmental cycle that yields a soluble extended PD (pi 11) that was processed into a p73 PD and a novel p30 fragment. Soluble PmpD peptides possess putative eukaryotic-interacting motifs suggesting potential secondary functions within or distal to infected cells. The multiple forms of PmpD could represent novel vaccine or drug targets. Taken together, these data implicate PmpD as a multifunctional virulence factor important in chlamydial pathogenesis.

Overall, these findings have contributed meaningful information related to the structure and function of CT153 and PmpD that will be useful for guiding future studies to determine their distinct roles in chlamydial pathogenesis.

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© Copyright 2009 Lacey Diane Taylor