RGD Reference Report - A plasminogen-like protein selectively degrades stearoyl-CoA desaturase in liver microsomes. - Rat Genome Database

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A plasminogen-like protein selectively degrades stearoyl-CoA desaturase in liver microsomes.

Authors: Heinemann, FS  Korza, G  Ozols, J 
Citation: Heinemann FS, etal., J Biol Chem 2003 Oct 31;278(44):42966-75. Epub 2003 Aug 19.
RGD ID: 1299253
Pubmed: PMID:12928439   (View Abstract at PubMed)
DOI: DOI:10.1074/jbc.M306240200   (Journal Full-text)

Stearoyl-CoA desaturase (SCD) is an integral membrane protein of the endoplasmic reticulum that is rapidly and selectively degraded when isolated liver microsomes are incubated at 37 degrees C. We previously reported the purification of a 90-kDa microsomal protein with SCD protease activity and characterized the inhibitor sensitivity of the protease. Here we show that the 90-kDa protein is a microsomal form of plasminogen (Pg) and that the purified SCD protease contains a spectrum of plasmin-like derivatives. The 90-kDa protein was identified as Pg by mass spectrometry of its tryptic peptides. The purified SCD protease reacted with Pg antibody, and immunoblotting demonstrated enrichment of Pg by the purification procedure established for the SCD protease. Analysis of microsomes by zymography demonstrated a single band of proteolytic activity at 70-kDa corresponding to the mobility of Pg in nonreduced polyacrylamide gels. When microsomes were incubated at 37 degrees C prior to zymography, an intense band of proteolytic activity developed at 30-kDa. The purified SCD protease displayed a spectrum of proteolytic bands ranging from 70 to 30 kDa. Degradation of SCD by the purified protease and by microsomes was inhibited by bdellin, a plasmin inhibitor from the medicinal leech Hirudo medicinalis. To explore the role of Pg in the degradation of SCD in vivo, we examined SCD expression and degradation in microsomes isolated from Pg-deficient (Pg-/-) mice. Compared with microsomes from wild-type littermate control mice, liver microsomes from Pg-/- mice had significantly higher levels of SCD. Degradation of SCD in microsomes from Pg-/- mice was markedly diminished, whereas liver microsomes from control mice showed rapid SCD degradation similar to that observed in rat liver microsomes. These findings indicate that SCD is degraded by a protease related to Pg and suggest that plasmin moonlights as an intracellular protease.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
proteolysis involved in protein catabolic process  IDA 1299253 RGD 

Molecular Function
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
endopeptidase activity  IDA 1299253 RGD 

Objects Annotated

Genes (Rattus norvegicus)
Plg  (plasminogen)

Objects referenced in this article
Gene Scd stearoyl-CoA desaturase Rattus norvegicus

Additional Information