Abstract
The rlp-1 gene is a member of the Rab small GTP-binding protein family. By using yeast two-hybrid analysis with rlp-1 as a bait, our laboratory has previously identified a cDNA clone encoding the small heat shock protein HSPB3 from a human fetal hippocampus library. A hybridoma that produces monoclonal antibody specific to this protein was also generated. By using western blot analysis, the protein was detected in rat kidney, brain, skeletal muscle and most abundantly in the heart. Among more than 10 different cell lines tested, COS-1 cells were found to produce the highest amount of HSPB3. A significant increase in the synthesis of HSPB3 was found upon stimuli of heat stress, heavy metal ions and serum starvation. Moreover, the cellular location of the protein was demonstrated using immunofluorescence analysis and subcellular fractionation. The HSPB3 was found to be distributed evenly in the endoplasmic reticulum and nucleolus of the COS-1 cells. The phosphorylation and structural organization of HSPB3 following serum stimulation of serum-starved COS-1 cells were also investigated. However, no difference in phosphorylation pattern and structural organization was noted between the starved and the refed cells. Finally, HSPB3 can prevent unfolded proteins from irreversible aggregation indicating that HSPB3 possesses a chaperone-like activity. These results provide basic information on the properties and the functional role of the heat shock protein, HSPB3.