We explored expression and possible function of interferon-γ (IFN-γ) in cultured fetal (E15) rat dorsal root ganglion neurons combining whole cell patch-clamp electrophysiology with single cell reverse transcriptase polymerase chain reaction and confocal laser immunocytochemistry. Morphologically, we located IFN-γ protein in the cytoplasm of the neurons in culture as well as in situ during peri- and postnatal development. Transcripts for classic IFN-γ and for its receptor were determined in probes of cytoplasm sampled from individual cultured neurons, which had been identified by patch clamp electrophysiology. In addition, the cultured neurons expressed both chains of the IFN-γ receptor.Locally produced IFN-γ acts back on its cellular source. Phosphorylation and nuclear translocation of the IFN-inducible transcriptional factor STAT1 as well as IFN-γ–dependent expression of major histocompatibility complex class I molecules on the neuronal membrane were noted in untreated cultures. However, both processes were substantially blocked in the presence of antibodies neutralizing IFN-γ. Our findings indicate a role of IFN-γ in autocrine regulation of sensory neurons.

Granzyme K (GzmK) belongs to a family of trypsin-like serine proteases localized in electron dense cytoplasmic granules of activated natural killer and cytotoxic T-cells. Like the related granzymes A and B, GzmK can trigger DNA fragmentation and is involved in apoptosis. We expressed the Ser 195 3 Ala variant of human proGzmK in Escherichia coli, crystallized it, and determined its 2.2-Å x-ray crystal structure. Pro-GzmK possesses a surprisingly rigid structure, which is most similar to activated serine proteases, in particular complement factor D, and not their proforms. The N-terminal peptide Met 14 -Ile 17 projects freely into solution and can be readily approached by cathepsin C, the natural convertase of pro-granzymes. The pre-shaped S1 pocket is occupied by the ion paired residues Lys 188B -Asp 194 and is hence not available for proper substrate binding. The Ser 214 -Cys 220 segment, which normally provides a template for substrate binding, bulges out of the active site and is distorted. With analogy to complement factor D, we suggest that this strand will maintain its nonproductive conformation in mature GzmK, mainly due to the unusual residues Gly 215 , Glu 219 , and Val 94 . We hypothesize that GzmK is proteolytically active only toward specific, as yet unidentified substrates, which upon approach transiently induce a functional activesite conformation.

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Tryptase-like activities of T and NK

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