Vancomycin is a widely prescribed antibiotic, but the exact nature of vancomycin-associated nephrotoxicity is unclear, in particular when considering the frequent coadministration of aminoglycosides. We describe here the initial case of a 56-year-old woman with normal renal function developing unexplained ARF without hypovolemia after administration of vancomycin without coadministration of aminoglycosides. Studying the patient’s renal biopsy specimen, we ascertained that obstructive tubular casts composed of noncrystal nanospheric vancomycin aggregates entangled with uromodulin explained the vancomycin-associated ARF. We developed in parallel a new immunohistologic staining technique to detect vancomycin in renal tissue and confirmed retrospectively that deleterious vancomycin-associated casts existed in eight additional patients with acute tubular necrosis in the absence of hypovolemia. Concomitant high vancomycin trough plasma levels had been observed in each patient. We also reproduced experimentally the toxic and obstructive nature of vancomycin-associated cast nephropathy in mice, which we detected using different in vivo imaging techniques. In conclusion, the interaction of uromodulin with nanospheric vancomycin aggregates represents a new mode of tubular cast formation, revealing the hitherto unsuspected mechanism of vancomycin-associated renal injury.

␤-arrestins (␤-arrs), two ubiquitous proteins involved in serpentine heptahelical receptor regulation and signaling, form constitutive homo-and heterooligomers stabilized by inositol 1,2,3,4,5,6-hexakisphosphate (IP6). Monomeric ␤-arrs are believed to interact with receptors after agonist activation, and therefore, ␤-arr oligomers have been proposed to represent a resting biologically inactive state. In contrast to this, we report here that the interaction with and subsequent titration out of the nucleus of the protooncogene Mdm2 specifically require ␤-arr2 oligomers together with the previously characterized nucleocytoplasmic shuttling of ␤-arr2. Mutation of the IP6-binding sites impair oligomerization, reduce interaction with Mdm2, and inhibit p53-dependent antiproliferative effects of ␤-arr2, whereas the competence for receptor regulation and signaling is maintained. These observations suggest that the intracellular concentration of ␤-arr2 oligomers might control cell survival and proliferation. bioluminescence resonance energy transfer ͉ FRET ͉ nucleocytoplasmic shuttling ͉ ubiquitination

No abstract