Identification of heat shock protein 70 in canine reticulocytes and mature erythrocytes

In the present study, we demonstrated that heat shock protein 70 (Hsp70) was present in both canine reticulocytes and mature erythrocytes, and that the canine Hsp70 in reticulocytes was decreased along with the maturation of the cells into erythrocytes. These results suggest that the Hsp70 in canine reticulocytes might act as a chaperone to remove unnecessary proteins during reticulocyte maturation. We also demonstrated that Hsp70 was present in exosomes from reticulocytes during their maturation in in vitro culture. Furthermore, the concentration of Hsp70 in reticulocyte membranes was increased in proportion to an increase of the protein in exosomes until 48 hours after the incubation of reticulocytes in vitro. At 96 hours of the incubation, however, only a trace amount of Hsp70 was detected in the membrane, while a large amount of the protein was present in the exosomes. These results suggest that Hsp70 in canine reticulocytes might play an important role for exosome formation in reticulocytes, resulting in the maturation of the cells.