The Host Cell Co-Chaperonin Hsp10 is an Interacting Partner for the Legionella pneumophila Multifunctional Chaperonin HtpB

L. pneumophila is an intracellular bacterium that replicates inside a membrane-bound vacuole called LegionellaContaining Vacuole (LCV), where it profusely releases its HtpB chaperonin. From LCV, HtpB reaches the host cell cytoplasm, where it interacts with SAMDC, a cytoplasmic protein required for synthesis of host polyamines that are important for intracellular growth of L. pneumophila. Moreover, cytoplasmic expression of HtpB in S. cerevisiae induces pseudohyphal growth, and in mammalian cells recruits mitochondria to LCV and modifies actin microfilaments organization. This led us to hypothesize here that HtpB recruits a protein(s) from eukaryotic cells that is involved in emergence of the aforementioned phenotypes. To identify this protein, a commercially available HeLa cDNA library was screened using a yeast two-hybrid system. Approximately 5 x 106 yeast clones carrying HeLa cDNA library plasmid were screened. Twenty one positive clones were identified. DNA sequence analysis revealed that all of these positive clones encoded the mammalian small heat shock protein Hsp10. Based on the fact that chaperonins are required to interact with co-chaperonins to function properly in protein folding, thus, HtpB may recruit the host cell Hsp10 to appropriately interact with SAMDC and to induce the cellular phenotypes deemed important for L. pneumophila pathogenesis.