Identification of Urinary CD44 and Prosaposin as Specific Biomarkers of Urinary Tract Infections in Children With Neurogenic Bladders

Forster, Catherine S; Haffey, Wendy D; Bennett, Michael; Greis, Kenneth D; Devarajan, Prasad

Prosaposin, a parent protein for the saposins, is a glycoprotein. Together with the saposins, it has multiple functions in the body including glycosphingolipid transport, facilitation of sphingolipid hydrolysis, 35 activation of glycosphingolipid synthesis, 36 as well as development and homeostasis of the male reproductive organs. 37 Prosaposin also exists as a secretory protein and has been described in milk, cerebrospinal fluid, and seminal fluid. 35 While the majority of the function of prosaposin, and the associated saposins, occurs within the context of the neurological system, the saposins also play a role within the immune system. Indeed, the saposins play a critical role in activation of invariate natural killer T cells through assisting access of CD1d cells to microbial molecules. 38 Furthermore, CD1d-mediated natural killer T-cell activation has been implicated in the host response to E coli UTIs. 39 Taken together with our data shown here, this suggests that prosaposin may facilitate the innate immune response to UTIs, thus partially explaining its role as a potential marker of UTI.