PREFERENTIAL LOCALIZATION OF HEAT-SHOCK PROTEIN-47 IN DILATED ENDOPLASMIC-RETICULUM OF CHICKEN CHONDROCYTES

We investigated the distribution of heat shock protein 47 (hsp47) in c ultured chicken embryonic chondrocytes and epiphyseal chondrocytes of tibial bones from 1-day-old to Ci-week-old chickens. Northern blot and immunoblot analyses revealed that hsp47 exists in epiphyseal cartilag e and cultured chondrocytes. Confocal laser immunofluorescence microsc opy showed that hsp47 was localized mainly in the many granular struct ures found in the cytoplasm that contain Type II collagen. Epiphyseal cartilage and cultured chondrocytes were embedded in LR White resin an d hsp47 was detected by protein A-immunogold electron microscopy. Gold particles were localized exclusively in the cisternal space of the en doplasmic reticulum (ER), and the labeling density of the cisternal sp ace of the dilated ER was always higher than that of the non-dilated E R. In all the differentiating zones of epiphyseal cartilage, the label ing density was highest in the hypertrophic cells. These findings sugg est that hsp47 plays an important role(s) in the synthesis, processing , and assembly of Type II collagen.