Protease nexin I expression is up-regulated in human skeletal muscle by injury-related factors.
Protease nexin I is a 43-50 kDa glycoprotein capable of inhibiting a number of serine proteases. In cultured differentiated human skeletal muscle (myotubes), we previously found that protease nexin I was localized in patches at their surface where it was active and able to inhibit thrombin. To understand the role of skeletal muscle protease nexin I after injury or in inflammatory conditions where thrombin might be extravasated by blood vessels, we examined the role of inflammatory factors on protease nexin I synthesis and secretion by myotubes in culture. By enzyme-linked immunosorbent assay (ELISA) and Western blotting, we found that this serine protease inhibitor is secreted by cultured human myotubes. Protease nexin I secretion is stimulated by tumor necrosis factor-alpha, transforming growth factor-beta and interleukin-1. Complex formation experiments with labeled thrombin reveal active protease nexin I bound to the surface of the treated cells. Secreted protease nexin I-thrombin complex was enhanced in the presence of transforming growth factor-beta and tumor necrosis factor-alpha. Protease nexin I mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis. Whatever the conditions, no significantly different levels were observed, indicating that the changes in cell and media protease nexin I concentration are elicited at the translational/posttranslational levels. Immunocytochemical studies on human skeletal muscle biopsies of patients suffering from inflammatory myopathies showed an overexpression of protease nexin I together with the above inflammatory factors. These findings suggest that skeletal muscle protease nexin I might play a role after injury or inflammatory pathologies.
Mbebi
C
C
INSERM Unité 523 (formerly 153), Institut de Myologie, Hôpital de la Salpêtrière, Paris, France.
Hantaï
D
D
Jandrot-Perrus
M
M
Doyennette
M A
MA
Verdière-Sahuqué
M
M
D016564:Amyloid beta-Protein Precursor; D001706:Biopsy; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000473:pathology; D002478:Cells, Cultured; D003470:Culture Media; D004797:Enzyme-Linked Immunosorbent Assay; D015971:Gene Expression Regulation, Enzymologic / Q000276:immunology; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D007455:Iodine / Q000494:pharmacology; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000293:injuries* / Q000473:pathology; D058255:Protease Nexins; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015842:Serine Proteinase Inhibitors / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014945:Wound Healing / Q000276:immunology
D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D003470:Culture Media; D007375:Interleukin-1; D058255:Protease Nexins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D015842:Serine Proteinase Inhibitors; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D007455:Iodine; D013917:Thrombin