Inhibitory p41 isoform of invariant chain and its potential target enzymes cathepsins L and H in distinct populations of macrophages in human lymph nodes.

Activation of the CD4(+) T-cell mediated immune response relies on the proteolytic capacity of enzymes involved in modulating major histocompatibility complex (MHC) II-associated antigen presentation in antigen-presenting cells (APC). The MHC II-associated chaperone molecule p41 isoform of invariant chain (inhibitory p41 Ii) has been suggested to regulate stability and activity of cathepsin L in these APC. In the present study the human lymph node distribution of non-inhibitory p31 Ii and inhibitory p41 Ii have been compared by differential labelling, using two specific monoclonal antibodies.

Individual recombinant thyroglobulin type-1 domains are substrates for lysosomal cysteine proteinases.

Thyroglobulin contains 11 repeats of a motif called thyroglobulin type-1 domain that show sequence similarity to some proteins exhibiting inhibitory activity against cysteine proteinases. Here we report that thyroglobulin decreases the activity of cathepsins B, H, L, and papain. To examine the possible involvement of particular type-1 domains in that decrease of activity, some individual thyroglobulin type-1 domains were expressed in E.

Anti-cathepsin L monoclonal antibodies that distinguish cathepsin L from cathepsin V.

Cathepsin L is a lysosomal cysteine protease involved in intracellular protein degradation. Recently, several new cysteine proteases have been identified. Human cathepsin V, a thymus- and testis-specific human cysteine protease, shares 78% sequence identity with human cathepsin L.

The cysteine protease activity of Colorado potato beetle (Leptinotarsa decemlineata Say) guts, which is insensitive to potato protease inhibitors, is inhibited by thyroglobulin type-1 domain inhibitors.

High levels of protease inhibitors are induced in potato leaves by wounding. These inhibitors, when ingested by Colorado potato beetle (Leptinotarsa decemlineata Say) larvae, induce expression of specific proteolytic activities in the gut. Induced protease activities cannot be inhibited by potato inhibitors and thus enable the insects to overcome this defence mechanism of potato plants.

Thyropins--new structurally related proteinase inhibitors.

Thyroglobulin type-1 domain is a structural element found in a variety of functionally unrelated proteins. It may occur singly, as in insulin-like growth factor binding proteins, or multiply up to eleven, as in thyroglobulin. Some of these type-1 domain containing proteins have been shown to have the ability to inhibit either cysteine or cation-dependent proteinases.