GLYCATION-DEPENDENT ALTERATION OF BASEMENT MEMBRANES

Project Details

Description

Chronic renal failure, characterized by proteinuria and alterations of
glomerular filtration rate, is a major complication of longstanding
diabetes mellitus. In this disorder, the glomerular basement membrane
(GBM) filtration barrier becomes increasingly permeable to large and
anionic proteins and, as both GBM and mesangial matrix become thicker,
filtration surface decreases. Three biochemical changes have been
identified in diabetic basement membranes (BMs): [1] an increase in the
extent of non-enzymatic glycosylation of component proteins, [2] an
increase in the covalent crosslinking of type IV collagen, and [3] a
decrease in the amount of heparan sulfate proteoglycan (HSPG) within the
GBM. While protein crosslinking may result in both sieving changes and
account for GBM thickening due to decreased degradation, the decrease in
HSPG is thought to explain the loss of the polyanionic sieving barrier. We propose to analyze the structure of diabetic BMs and explore the
hypothesis that accelerated non-enzymatic glycosylation (glycation), a
direct consequence of chronic hyperglycemia in which ketoamine and
crosslinks form in proteins, plays a major role in the alteration of the
molecular architecture and dependent sieving function of BMs in diabetes.
These studies will be conducted in the context of a newly developed model
for BM structure and function from our laboratory. In particular we will
focus on the supromolecular organization of BM collagen, laminin and
glycosaminoglycan. (A) We will compare normal, diabetic and experimentally
glycated collagen structure in GBM: here we will employ electron
microscopy of high resolution platinum/carbon replicas and X-ray
diffraction. (B) We will evaluate the ketoamines and crosslinks in
diabetic and experimentally glycated GBM by a variety of biochemical and
biophysical techniques (proteolytic solubilization, ketoamine and
fluorescence crosslink characterization, fragment size analysis, and
protein domain identification). (C) We will evaluate the consequences of
glycation on the polymerization of laminin and its interaction with
proteoglycan using assays we have developed for the study of normal BM
assembly. With this approach we expect to be able to construct models for
the alterations which occur in BM molecular architecture.
StatusFinished
Effective start/end date2/1/901/31/95

Funding

  • National Institutes of Health
  • National Institutes of Health: $88,301.00
  • National Institutes of Health
  • National Institutes of Health: $100,508.00
  • National Institutes of Health

ASJC

  • Medicine(all)

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