RGD Reference Report - Heat shock protein 72, a chaperone abundant in renal papilla, counteracts urea-mediated inhibition of enzymes. - Rat Genome Database

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Heat shock protein 72, a chaperone abundant in renal papilla, counteracts urea-mediated inhibition of enzymes.

Authors: Neuhofer, W  Fraek, ML  X Beck, F 
Citation: Neuhofer W, etal., Pflugers Arch 2002 Oct;445(1):67-73. Epub 2002 Sep 19.
RGD ID: 1300068
Pubmed: PMID:12397389   (View Abstract at PubMed)
DOI: DOI:10.1007/s00424-002-0858-1   (Journal Full-text)

Urea, at concentrations routinely observed in the renal inner medulla during antidiuresis in many mammals, is a potent protein destabilizing agent that reduces the activity of many enzymes. The molecular chaperone heat shock protein 72 (HSP72) is expressed at about 5 ng/ micro g protein in the renal papilla and is thus 40 times more abundant than in the isosmotic cortex and may counteract the deleterious effects of high urea concentrations in the inner medulla. To test this hypothesis, we examined the effect of recombinant HSP72 on lactate dehydrogenase activity in the presence of 0.8 M urea in a cell-free system. The urea-induced increase in K(m) was reduced by 85% in the presence of 1 microM HSP72 but only by 6% by 100 mM betaine, a "counteracting" trimethylamine osmolyte. Conversely, the decrease in V(max) with 0.8 M urea was not affected by HSP72 but was attenuated by 42% in the presence of betaine. The protective effect of HSP72 was confirmed by the attenuation of the urea-induced decrease in the activity of another model enzyme, beta-galactosidase, by lysate of HSP72-overexpressing MDCK cells. Hence, in addition to the trimethylamine osmolytes, HSP72 may participate in counteracting urea-mediated effects on protein function in the renal papilla.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
response to unfolded protein  IMP 1300068 RGD 

Objects Annotated

Genes (Rattus norvegicus)
Hspa1a  (heat shock protein family A (Hsp70) member 1A)


Additional Information