Differential Proteomics of Urinary Exovesicles from Classical Galactosemic Patients Reveals Subclinical Kidney Insufficiency.
Classical galactosemia is caused by a nearly complete deficiency of galactose-1-phosphate uridyltransferase (GALT; EC 2.7.712), resulting in a severely impaired galactose metabolism with galactose-1-phosphate and galactitol accumulation. Even on a galactose-restricted diet, patients develop serious long-term complications of the central nervous system and ovaries that may result from chronic cell-toxic effects exerted by endogenous galactose. To address the question of whether disease-associated cellular perturbations could affect the kidney function of the patients, we performed differential proteomics of detergent-resistant membranes from urinary exovesicles. Galactosemic samples (showing drastic shifts from high-mannose to complex-type N-glycosylation on exosomal N-glycoproteins) and healthy, sex-matched controls were analyzed in quadruplex iTRAQ experiments performed in biological and technical replicates. Particularly in the female patient group, the most striking finding was a drastic increase of abundant serum (glyco)proteins, like albumin, leucine-rich α-2-glycoprotein, fetuin, immunoglobulins, prostaglandin H2 d-isomerase, and α-1-microglobulin protein (AMBP), pointing to a subclinical failure of kidney filter function in galactosemic patients and resulting in a heavy overload of exosomal membranes with adsorbed serum (glyco)proteins. Several of these proteins are connected to TBMN and IgAN, proteinuria, and renal damage. The impairment of renal protein filtration was also indicated by increased protein contents derived from extracellular matrices and lysosomes.
Institute of Biochemistry II, Medical Faculty, University of Cologne , Köln, D-50931, Germany.
Simon
S
Staubach
Institute of Biochemistry II, Medical Faculty, University of Cologne , Köln, D-50931, Germany.
Murat
M
Pekmez
Institute of Biochemistry II, Medical Faculty, University of Cologne , Köln, D-50931, Germany.|Center for Molecular Medicine Cologne, University of Cologne , Köln, D-50931 Germany.
Franz-Georg
FG
Hanisch
D000328:Adult; D016022:Case-Control Studies; D005109:Extracellular Matrix / Q000737:chemistry; D000067128:Extracellular Vesicles / Q000737:chemistry*; D005260:Female; D005693:Galactosemias / Q000150:complications* / Q000175:diagnosis; D006023:Glycoproteins / Q000032:analysis; D006031:Glycosylation; D006801:Humans; D007668:Kidney / Q000293:injuries; D008247:Lysosomes / Q000737:chemistry; D008297:Male; D020543:Proteome / Q000032:analysis*; D040901:Proteomics / Q000379:methods; D051437:Renal Insufficiency / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism; D014556:Urine / Q000166:cytology
D006023:Glycoproteins; D020543:Proteome
classical galactosemia; cubilin−megalin complex; differential proteomics; iTRAQ; membrane raft protein; urinary exosomes