A Novel System of Cytoskeletal Elements in the Human Pathogen Helicobacter pylori

Abstract

Pathogenicity of the human pathogen Helicobacter pylori relies upon its capacity to adapt to a hostile environment and to escape from the host response. Therefore, cell shape, motility, and pH homeostasis of these bacteria are specifically adapted to the gastric mucus. We have found that the helical shape of H. pylori depends on coiled coil rich proteins (Ccrp), which form extended filamentous structures in vitro and in vivo, and are differentially required for the maintenance of cell morphology. We have developed an in vivo localization system for this pathogen. Consistent with a cytoskeleton-like structure, Ccrp proteins localized in a regular punctuate and static pattern within H. pylori cells. Ccrp genes show a high degree of sequence variation, which could be the reason for the morphological diversity between H. pylori strains. In contrast to other bacteria, the actin-like MreB protein is dispensable for viability in H. pylori, and does not affect cell shape, but cell length and chromosome segregation. In addition, mreB mutant cells displayed significantly reduced urease activity, and thus compromise a major pathogenicity factor of H. pylori. Our findings reveal that Ccrp proteins, but not MreB, affect cell morphology, while both cytoskeletal components affect the development of pathogenicity factors and/or cell cycle progression.

Phosphorylation of a Novel Cytoskeletal Protein (RsmP) Regulates Rod-shaped Morphology in Corynebacterium glutamicum

“…The filaments formed were confirmed by transmission electron microscopy (Fig. 7); they appeared similar to the filaments described for the Ccrp59 (coiled-coil rich proteins) from H. pylori (30). RsmP formed straight and branched filamentous structures measuring on average 2000 nm long and 50 nm diameter, thus definitively confirming its function as a cytoskeletal protein.…”

“…Phylogenetic analyses were conducted in MEGA4 (70). the conditional mutant phenotype showing that RsmP (Cg3264) is involved in polar growth or rod-shaped determination, we hypothesized that RsmP could support cell shape by forming intracellular filaments or a bacterial cytoskeleton like CreS, FilP, or Ccrp (29,30,46). To test this hypothesis, we cloned rsmP into the E. coli/corynebacterial shuttle plasmid pEAG6 designed to easily clone and overexpress any promoterless gene under the control of the Pdiv promoter and fused to egfp2 (23), thus generating pE_RsmP-GFP.…”

“…Bagchi et al (29) demonstrated the existence of another IF protein (FilP or SCO5396) forming cytoskeletal structures in S. coelicolor, which were involved in the mechanical strength of the hyphae and required for normal growth and morphogenesis. In addition, Waidner et al (30) showed that the helical shape of the human pathogen Helicobacter pylori was dependent on coiled-coil-rich proteins (Ccrp59 and Ccrp1143), which form filamentous structures in vitro and in vivo. Interestingly, CreS, FilP, and eukaryotic IF proteins share a central "rod domain" of four alternating coiled-coil segments and linkers, flanked by more globular head (N-terminal) and tail (C-terminal) domains, with the rod domain being essential for filament formation (31).…”

“…Interestingly, CreS, FilP, and eukaryotic IF proteins share a central "rod domain" of four alternating coiled-coil segments and linkers, flanked by more globular head (N-terminal) and tail (C-terminal) domains, with the rod domain being essential for filament formation (31). In contrast, Ccrps are almost entirely composed of coiled coils and lacks the characteristic head and tail domains (30). The most important feature of coiled-coil domains appears to be their ability to act as a "cellular Velcro" to hold together molecules, subcellular structures, and even tissues in higher organisms.…”

Localization of FtsZ in Helicobacter pylori and Consequences for Cell Division

“…To this end, we used our previously developed system (14) that permits in vivo localization of individual proteins in H. pylori. Our results indicate that the H. pylori FtsZ ring is positioned with very little precision, resulting in daughter cells showing considerably different sizes.…”