Identification of Staphylococcal Enterotoxin B Domains Involved in Binding to Cultured Human Kidney Proximal Tubular Cells: Imparting Proliferation and Death

Abstract

Studies suggest that staphylococcal enterotoxin B (SEB) is initially harbored in the kidney by binding to digalactosylceramide molecules in the proximal tubular cells. However, little is known in regard to the peptide motif within SEB that binds to these cells and imparts toxic effects. Herein, using human kidney proximal tubular cells (PTs) we have performed a systematic study on the binding of various peptides and peptide analogs of SEB and demonstrate a structure-functional relationship. Using [(125)I]labeled SEB peptides, we show a high affinity and displaceable binding of SEB 191-220 to human PT cells. Binding was mitigated by the use of antibody against SEB, by digalactosylceramide (the putative receptor), and by the use of endoglycoceramidase, which selectively removes the oligosaccharide backbones from glycosphingolipids. Our structure/ functional studies revealed that peptide 130-160 induces a concentration-dependent increase in programmed cell death/ apoptosis in human proximal tubular cells. Mechanistic studies further suggest that SEB/SEB peptide (130-160) impart apoptosis via the activation of neutral sphingomyelinase, which hydrolizes sphingomyelin to ceramide and phosphocholine. SEB 130-160 mediated apoptosis was mitigated by preincubation of cells with antibody against SEB and an SEB 130-160 antibody.

Blood Groups in Infection and Host Susceptibility

“…Domain II (aa 127 to 239) contains the T-cell receptor binding site and a "␤-grasp" motif composed of six antiparallel ␤-sheets. Surprisingly, the galabiosylceramide lectin domain is localized in domain II (aa 191 to 220), immediately adjacent to the T-cell binding site (aa 210 to 214) (470,471). The ␤-grasp motif is present among many bacterial proteins involved in Gram-positive cell wall synthesis and is believed to be a conserved, ancestral polysaccharide/sugar binding domain (472).…”

“…The ␤-grasp motif is present among many bacterial proteins involved in Gram-positive cell wall synthesis and is believed to be a conserved, ancestral polysaccharide/sugar binding domain (472). Sequences in domain II (aa 130 to 160) have also been linked to apoptosis, possibly through the sphingomyelinase/ceramide signaling pathway (471,473).…”

Ceramide-Induced Apoptosis in Renal Tubular Cells: A Role of Mitochondria and Sphingosine-1-Phoshate

“…Ceramide is generated and accumulated in RTCs in response to various stimuli ( Table 1 ). In vitro studies show that such stimuli include hypoxia/reoxygenation [ 31 , 32 , 50 , 51 , 52 ], oxidants [ 33 , 53 , 54 ], UV light [ 38 , 39 , 55 ], heat stress [ 56 ], oxalate [ 54 , 57 ], P-fimbriae of E. coli [ 58 , 59 ], nephrotoxins, including cadmium [ 60 , 61 ], isoflurane [ 62 ], microcystin [ 63 ], nickel [ 64 ], and radiocontrast [ 65 ], Shiga-toxin B [ 58 ], staphylococcal enterotoxin B [ 66 ], interleukin (IL)-1β [ 59 ] and TNF-α [ 54 , 59 ]. In vivo studies show that ceramide is accumulated in kidneys exposed to anti-glomerular membrane (GBM) antibody [ 52 ], nephrotoxins such as carbon tetrachloride [ 67 ] and isoflurane [ 62 ], developing kidney [ 68 , 69 ], ischemia/reperfusion (I/R) injury [ 51 , 52 ], glycerol-induced myohemoglobinuria [ 52 ], and obstructive nephropathy [ 70 ].…”

Characterization of the interaction of staphylococcal enterotoxin B with CD1d expressed in human renal proximal tubule epithelial cells

“…Multiple studies reported the critical protective role played by the kidney in excretion of SEB [ 20 - 26 ]. RPTECs selectively express CD1d, which play a significant ( and MHC II-independent) role in antigen sensing and recognition process [ 13 , 29 - 31 ]. The present study sought to elucidate the renal pathogenesis of SEB with the primary focus on the toxin’s interaction with CD1d expressed on RPTECs.…”

“…The present study is focused on CD1d for two primary reasons. Firstly, CD1d selectively expressed in the renal epithelial tissues are recruited for antigen sensing, recognition and cleansing at the late stage of pathogenesis [ 13 , 28 - 31 ]. Unlike a typical host-mediated antigen recognition sequence, the intact sAgs are submitted to the antigen presenting cells (APC) by CD1d, a phylogenetic analog of major histocompatibility complex (MHC) class I and II molecules operating as an antigen-trafficking agent [ 32 - 34 ].…”