Characteristics of the Phagocytic Cup Induced by Uropathogenic Escherichia coli

Abstract

S U M M A R Y Uropathogenic Escherichia coli invade the urothelial umbrella cells by using the zipper mechanism. However, the details of the early events of this invasion, such as the formation of the phagocytic cup, are not yet well understood. We show here, using thin section electron microscopy and immunogold labeling, that the plasma membrane curves around the bacterial surface in the phagocytic cup. There exists a uniform gap between the bacterium and the urothelial membrane, and actin filaments are present in the phagocytic cup. We suggest that the action-reaction between the mechanical forces generated by pilus retraction of the bacterium and the actin polymerization in the urothelial cell plays a role in maintaining the phagocytic cup. This manuscript contains online supplemental material at

Cell biology and physiology of the uroepithelium

“…This would recruit extra UPIa receptors at the bacterial-host cell interface and provide additional membrane to surround the bacterium, in what is likely to be an actin-dependent process (226). As the membrane coalesces around the bacteria, there is formation of tubular invaginations and then a vacuole-like compartment with attached membranous tethers, which may result from collapse of the tubular membrane around the bacteria (28).…”

“…The membrane associated with the hinge and plaque regions is highly detergent insoluble (138), likely reflecting the unusual lipid composition of this membrane, which is similar to myelin and rich in cholesterol, phosphatidylcholine, phosphatidylethanolamine, and cerebroside (86). Relative to the basolateral surface, only a small amount of actin is associated with the apical pole of the umbrella cell, and the apical plasma membrane may be devoid of actin (172,226). However, other studies show that small amounts of filamentous actin are variably associated with the apical pole of the umbrella cell (cf.…”

Persistence of Uropathogenic Escherichia coli in the Face of Multiple Antibiotics

“…UPEC entry into bladder epithelial cells occurs via an actinand microtubule-dependent process that is mediated by type 1 pili, which are filamentous adhesive organelles that are encoded by virtually all UPEC isolates (10,38,60). The FimH adhesin associated with the distal tips of type 1 pili binds mannose-containing glycoprotein host receptors, which include uroplakin (specifically UP1a) and ␣3␤1 integrin complexes (16,63).…”

“…The FimH adhesin associated with the distal tips of type 1 pili binds mannose-containing glycoprotein host receptors, which include uroplakin (specifically UP1a) and ␣3␤1 integrin complexes (16,63). Uroplakin plaques coat nearly the entire lumenal surface of the bladder, and their internalization likely facilitates UPEC entry into terminally differentiated superficial bladder cells (5,41,43,45,60,63). Alternately, ␣3␤1 integrin receptor complexes, which are more widely expressed within the urothelium and elsewhere, can mediate UPEC invasion of less mature bladder cells via a clathrin-dependent pathway (15,16).…”

Uropathogenic Escherichia coli Invades Host Cells via an HDAC6-modulated Microtubule-dependent Pathway

“…Among bacteria that enter host cells by a zipper-like mechanism are strains of uropathogenic E. coli (UPEC) 2 (2)(3)(4). These microbes are the major cause of urinary tract infections (UTIs), accounting for greater than 80% of cases worldwide (5,6).…”