Internalization of a polysialic acid-binding Escherichia coli bacteriophage into eukaryotic neuroblastoma cells

Abstract

Eukaryotic organisms are continuously exposed to bacteriophages, which are efficient gene transfer agents in bacteria. However, bacteriophages are considered not to pass the eukaryotic cell membrane and enter nonphagocytic cells. Here we report the binding and penetration of Escherichia coli PK1A2 bacteriophage into live eukaryotic neuroblastoma cells in vitro. The phage interacts with cell surface polysialic acid, which shares structural similarity with the bacterial phage receptor. Using fluorescence and electron microscopy, we show that phages are internalized via the endolysosomal route and persist inside the human cells up to one day without affecting cell viability. Phage capsid integrity is lost in lysosomes, and the phage DNA is eventually degraded. We did not detect the entry of phage DNA into the nucleus; however, we speculate that this might occur as a rare event, and propose that this potential mechanism could explain prokaryote–eukaryote gene flow.

Phage composition of a fermented milk and colostrum product assessed by microbiome array; putative role of open reading frames in reference to cell signaling and neurological development

“…It may be argued that mitogenic, signal-transducing G-proteins are localized inside cells as they are attached to the internal layer of the membrane through isoprenyl moieties, fatty acyl moieties, and electrostatic interactions (72), and they are therefore inaccessible to phage proteins. Such an argument however has been recently disproved by demonstration that phages are actually capable of penetrating into human cancer cells and remain active inside cells for at least 24h (73). Another argument against a role for phage proteins as tools against molecular carcinogenesis consists in the fact that ingested phages reside in the gastrointestinal tract and would therefore prove irrelevant for cancers arising in other parts of the body.…”

“…Another argument against a role for phage proteins as tools against molecular carcinogenesis consists in the fact that ingested phages reside in the gastrointestinal tract and would therefore prove irrelevant for cancers arising in other parts of the body. However, this argument was also disproved by observation that in animals and humans, phages translocate from the gut to other organs (74); this phenomenon, coupled with the ability of phages to penetrate into eukaryotic cells, is probably responsible for the continuous and dynamic virus-prokaryote-eukaryote gene flow (73). As a matter of fact, ingested phages have been found in sera of healthy individuals since 1971 (75).…”

Alterations in Enteric Virome Are Associated With Colorectal Cancer and Survival Outcomes

“…Bacteriophages might affect cancer cell behavior by shaping the bacterial microbiome or via direct transcytosis into colonic epithelial cells, thereby affecting tumor growth and invasiveness and ultimately the survival outcome of CRC patients. 84,85 Continued efforts in multikingdom profiling coupled with functional studies of the human gut microbiome in the field are needed to provide new mechanistic insights into how the microbial dark matter of the human gut metagenome contributes to our health and disease.…”

Pf Bacteriophage and Their Impact on Pseudomonas Virulence, Mammalian Immunity, and Chronic Infections

“…Together, these data suggest that lytic phages may promote opposite effects on bacterial clearance compared to Pf. The mechanistic basis for the differences and similarities seen between lytic and lysogenic phages is unclear, particularly since lytic phage are also internalized by eukaryotic cells (159). However, there are recent examples; enteric Caudovirales phages (tailed phages that package linear dsDNA) initially purified for therapeutic use were found to stimulate increased production of pro-inflammatory cytokines (119).…”