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Preferential localization of heat shock protein 47 in dilated endoplasmic reticulum of chicken chondrocytes
K Kambe1, A Yamamoto, T Yoshimori
1Department of Physiology, Kansai Medical University, Osaka, Japan.
Insights
Heat shock protein 47 (hsp47) aids in the synthesis and processing of Type II collagen in chicken chondrocytes. This protein is found in the endoplasmic reticulum, particularly in hypertrophic cells.
Area of Science:
- Cell Biology
- Biochemistry
- Developmental Biology
Background:
- Heat shock protein 47 (hsp47) is crucial for collagen processing.
- Type II collagen is essential for cartilage formation and integrity.
Purpose of the Study:
- To investigate the distribution and localization of hsp47 in chicken chondrocytes.
- To elucidate the role of hsp47 in Type II collagen synthesis and processing.
Main Methods:
- Northern blot and immunoblot analyses for hsp47 expression.
- Confocal laser immunofluorescence microscopy for subcellular localization.
- Protein A-immunogold electron microscopy for precise localization within the endoplasmic reticulum.
Main Results:
- hsp47 was detected in epiphyseal cartilage and cultured chondrocytes.
- hsp47 co-localized with Type II collagen in cytoplasmic granular structures.
- Electron microscopy revealed hsp47 exclusively within the endoplasmic reticulum (ER) cisternal space, with higher density in dilated ER and hypertrophic cells.
Conclusions:
- hsp47 is involved in the synthesis, processing, and assembly of Type II collagen.
- The localization of hsp47 within the ER suggests a role in collagen folding and modification.
- hsp47 expression is particularly high in hypertrophic chondrocytes, indicating its importance during cartilage differentiation.
Abstract:
We investigated the distribution of heat shock protein 47 (hsp47) in cultured chicken embryonic chondrocytes and epiphyseal chondrocytes of tibial bones from 1-day-old to 6-week-old chickens. Northern blot and immunoblot analyses revealed that hsp47 exists in epiphyseal cartilage and cultured chondrocytes. Confocal laser immunofluorescence microscopy showed that hsp47 was localized mainly in the many granular structures found in the cytoplasm that contain Type II collagen. Epiphyseal cartilage and cultured chondrocytes were embedded in LR White resin and hsp47 was detected by protein A-immunogold electron microscopy. Gold particles were localized exclusively in the cisternal space of the endoplasmic reticulum (ER), and the labeling density of the cisternal space of the dilated ER was always higher than that of the non-dilated ER. In all the differentiating zones of epiphyseal cartilage, the labeling density was highest in the hypertrophic cells. These findings suggest that hsp47 plays an important role(s) in the synthesis, processing, and assembly of Type II collagen.