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Invariant chain controls the activity of extracellular cathepsin L.

Fiebiger E, Maehr R, Villadangos J, Weber E, Erickson A, Bikoff E, Ploegh HL, Lennon-Duménil AM - J. Exp. Med. (2002)

Bottom Line: We detected mature CatL as a complex with p41(65aa) in culture supernatants from antigen-presenting cells (APCs).Despite the neutral pH of the extracellular milieu, released CatL associated with p41(65aa) is catalytically active as demonstrated by active site labeling and elastin degradation assays.We propose that p41(65aa) stabilizes CatL in the extracellular environment and induces a local increase in the concentration of matrix-degrading enzymes during inflammation.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

ABSTRACT
Secretion of proteases is critical for degradation of the extracellular matrix during an inflammatory response. Cathepsin (Cat) S and L are the major elastinolytic cysteine proteases in mouse macrophages. A 65 amino acid segment of the p41 splice variant (p41(65aa)) of major histocompatibility complex class II-associated invariant chain (Ii) binds to the active site of CatL and permits the maintenance of a pool of mature enzyme in endosomal compartments of macro-phages and dendritic cells (DCs). Here we show that interaction of p41(65aa) with mature CatL allows extracellular accumulation of the active enzyme. We detected mature CatL as a complex with p41(65aa) in culture supernatants from antigen-presenting cells (APCs). Extracellular accumulation of mature CatL is up-regulated by inflammatory stimuli as observed in interferon (IFN)-gamma-treated macrophages and lipopolysaccharide (LPS)-activated DCs. Despite the neutral pH of the extracellular milieu, released CatL associated with p41(65aa) is catalytically active as demonstrated by active site labeling and elastin degradation assays. We propose that p41(65aa) stabilizes CatL in the extracellular environment and induces a local increase in the concentration of matrix-degrading enzymes during inflammation. Through its interaction with CatL, Ii may therefore control the migratory response of APCs and/or the recruitment of effectors of the inflammatory response.

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Expression and release of CatL from resting and activated DCs. (A) Levels of intracellular CatL are slightly downregulated by DC activation. (B) Significantly larger amounts of mature CatL accumulate in supernatants from activated DCs. Reprobing of the membrane shows modest upregulation of proCatD secretion during activation.
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fig2: Expression and release of CatL from resting and activated DCs. (A) Levels of intracellular CatL are slightly downregulated by DC activation. (B) Significantly larger amounts of mature CatL accumulate in supernatants from activated DCs. Reprobing of the membrane shows modest upregulation of proCatD secretion during activation.

Mentions: Do these observations extend to bone marrow–derived DCs? We show that DCs also require the presence of intracellular p41 for expression of mature-24 kD CatL (13; Fig. 2 A). In line with this result, we find that extracellular accumulation of mature CatL is impaired in DCs that lack p41 (Fig. 2 B). In addition, significantly larger amounts of mature-24 kD CatL are detected in supernatants collected from LPS-activated DCs (Fig. 2 B).


Invariant chain controls the activity of extracellular cathepsin L.

Fiebiger E, Maehr R, Villadangos J, Weber E, Erickson A, Bikoff E, Ploegh HL, Lennon-Duménil AM - J. Exp. Med. (2002)

Expression and release of CatL from resting and activated DCs. (A) Levels of intracellular CatL are slightly downregulated by DC activation. (B) Significantly larger amounts of mature CatL accumulate in supernatants from activated DCs. Reprobing of the membrane shows modest upregulation of proCatD secretion during activation.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2194106&req=5

fig2: Expression and release of CatL from resting and activated DCs. (A) Levels of intracellular CatL are slightly downregulated by DC activation. (B) Significantly larger amounts of mature CatL accumulate in supernatants from activated DCs. Reprobing of the membrane shows modest upregulation of proCatD secretion during activation.
Mentions: Do these observations extend to bone marrow–derived DCs? We show that DCs also require the presence of intracellular p41 for expression of mature-24 kD CatL (13; Fig. 2 A). In line with this result, we find that extracellular accumulation of mature CatL is impaired in DCs that lack p41 (Fig. 2 B). In addition, significantly larger amounts of mature-24 kD CatL are detected in supernatants collected from LPS-activated DCs (Fig. 2 B).

Bottom Line: We detected mature CatL as a complex with p41(65aa) in culture supernatants from antigen-presenting cells (APCs).Despite the neutral pH of the extracellular milieu, released CatL associated with p41(65aa) is catalytically active as demonstrated by active site labeling and elastin degradation assays.We propose that p41(65aa) stabilizes CatL in the extracellular environment and induces a local increase in the concentration of matrix-degrading enzymes during inflammation.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

ABSTRACT
Secretion of proteases is critical for degradation of the extracellular matrix during an inflammatory response. Cathepsin (Cat) S and L are the major elastinolytic cysteine proteases in mouse macrophages. A 65 amino acid segment of the p41 splice variant (p41(65aa)) of major histocompatibility complex class II-associated invariant chain (Ii) binds to the active site of CatL and permits the maintenance of a pool of mature enzyme in endosomal compartments of macro-phages and dendritic cells (DCs). Here we show that interaction of p41(65aa) with mature CatL allows extracellular accumulation of the active enzyme. We detected mature CatL as a complex with p41(65aa) in culture supernatants from antigen-presenting cells (APCs). Extracellular accumulation of mature CatL is up-regulated by inflammatory stimuli as observed in interferon (IFN)-gamma-treated macrophages and lipopolysaccharide (LPS)-activated DCs. Despite the neutral pH of the extracellular milieu, released CatL associated with p41(65aa) is catalytically active as demonstrated by active site labeling and elastin degradation assays. We propose that p41(65aa) stabilizes CatL in the extracellular environment and induces a local increase in the concentration of matrix-degrading enzymes during inflammation. Through its interaction with CatL, Ii may therefore control the migratory response of APCs and/or the recruitment of effectors of the inflammatory response.

Show MeSH
Related in: MedlinePlus