Roles of Ca2+ and F-actin in intracellular aggregation of Chlamydia trachomatis in eucaryotic cells.
The effect of intracellular free Ca2+ ([Ca2+]i) on the intracellular aggregation of Chlamydia trachomatis serovars L2 and E in McCoy and HeLa cells is investigated. Loading the cells with the Ca2+ chelator MAPT/AM (1,2-bis-5-methyl-amino-phenoxylethane-N,N-n'-tetra-acetoxymethyl acetate), thereby decreasing the [Ca2+]i from 67 to 19 nM, decreased the number of cells with a local aggregation of chlamydiae in a dose-dependent manner. Neither the attachment nor the uptake of elementary bodies (EBs) was, however, affected after depletion of Ca2+ from the cells. There was no significant difference in the level of measured [Ca2+]i between infected and uninfected cells. Reducing the [Ca2+]i also significantly inhibited chlamydial inclusion formation. Differences in the organization of the actin filament network were observed in response to [Ca2+]i depletion. In Ca(2+)-depleted cells, where few EB aggregates were formed, few local accumulations of F-actin were observed in the cytosol. These results suggest that the aggregation of EBs in eucaryotic cells requires a normal homeostasis of intracellular Ca2+. By affecting F-actin reorganization and putatively certain Ca(2+)-binding proteins, [Ca2+]i plays a vital role in the infectious process of chlamydiae.
Majeed
M
M
Department of Clinical Microbiology, University of Linköping, Sweden.
Gustafsson
M
M
Kihlström
E
E
Stendahl
O
O
D000199:Actins / Q000502:physiology*; D001422:Bacterial Adhesion; D002118:Calcium / Q000502:physiology*; D002451:Cell Compartmentation; D002690:Chlamydia Infections / Q000473:pathology* / Q000503:physiopathology; D002692:Chlamydia trachomatis / Q000166:cytology*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques
D000199:Actins; D002118:Calcium