Faculty Collaboration Database

Loss of albumin and megalin binding to renal cubilin in rats results in albuminuria after total body irradiation. Am J Physiol Regul Integr Comp Physiol 2002 Aug;283(2):R339-46

Date

07/18/2002

Pubmed ID

12121845

DOI

10.1152/ajpregu.00752.2001

Scopus ID

2-s2.0-0036340308 (requires institutional sign-in at Scopus site)   23 Citations

Abstract

The role of the renal apical brush-border membrane (BBM) endocytic receptors cubilin and megalin in the onset of albuminuria in rats exposed to a single dose of total body irradiation (TBI) has been investigated. Albuminuria was evident as immunoblot (IB) analysis of the urine samples from TBI rats revealed excretion of large amounts of albumin. IB analysis of the BBM proteins did not reveal any significant changes in cubilin or megalin levels, but (125)I-albumin binding to BBM from TBI rats declined by 80% with a fivefold decrease (from 0.5 to 2.5 microM) in the affinity for albumin. IB analysis of cubilin from the BBM demonstrated a 75% loss when purified using albumin, but not intrinsic factor (IF)-cobalamin (Cbl) ligand affinity chromatography. Immunoprecipitation (IP) of Triton X-100 extract of the BBM with antiserum to cubilin followed by IB of the immune complex with an antiserum to megalin revealed a 75% loss of association between megalin and cubilin. IP studies with antiserum to cubilin or megalin and IB with antiserum to the cation-independent mannose 6-phosphate/insulin-like growth factor II-receptor (CIMPR) revealed that CIMPR interacted with both cubilin and megalin. In addition, TBI did not disrupt the association of CIMPR with either cubilin or megalin in BBM. These results suggest that albuminuria noted in TBI rats is due to selective loss of albumin and megalin, but not CIMPR or IF-Cbl binding by cubilin. Furthermore, these results also suggest that albumin and IF-Cbl binding to cubilin occur at distinct sites and that in the rat renal BBM, CIMPR interacts with both cubilin and megalin.

Author List

Yammani RR, Sharma M, Seetharam S, Moulder JE, Dahms NM, Seetharam B

Author

Nancy M. Dahms PhD Professor in the Biochemistry department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Albuminuria
Animals
Binding, Competitive
Chromatography, Affinity
Immunoblotting
Intrinsic Factor
Kidney
Low Density Lipoprotein Receptor-Related Protein-2
Male
Microvilli
Precipitin Tests
Protein Binding
Rats
Rats, Inbred Strains
Receptor, IGF Type 2
Receptors, Cell Surface
Serum Albumin
Vitamin B 12
Whole-Body Irradiation