Abstract
Purpose::
Crystallins seemed to have evolved from preexisting proteins that recruited to new structural roles in the lens. α-crystallins resemble heat-shock proteins with chaperone functions and ß/γ superfamily shows similarities to bacterial core protein. Although ß and γ-Crystallins had been considered for a long time to be present only in the ocular lens and structural protein to maintain the transparency of lens, expression of non lens tissues in normal and pathological state was indicated recently. However, nonrefractive function for these crystallins has not been indicated. In this study, we are trying to characterize ßB2, ßA1/A3 and γC -Crystallin expressed in non-lens tissues and investigate the potential role of these crystallins.
Methods::
Crystallins expressed in non-lens tissues were examined by immunoblotting analysis of proteins extracted from lens, retina, heart, kidney, skeletal muscle, and testis of adult C57BL/6J mouse. ßB2-crystallin mRNA in mouse organs was examined by RT-PCR. Immunohistochemical study was performed by using cryosections of various tissues mentioned above. Cellular localization of ßB2, ßA1/A3 and γC-Crystallin was investigated in migrating lens epithelial cells isolated from porcine lens. Furthermore, to investigate the ßB2-crystallin function in various organs, bB2-crystallin knockdown mice were generated.
Results::
ßB2 and ßA1/A3-Crystallins were expressed in lens, cerebrum, cerebellum, retina, heart, aorta, lung, kidney, and skeletal muscle. On the other hand, γC- Crystallin was observed in all tissue. ßB2-crystalllin mRNA is present in mouse lens, retina, cerebrum, cerebellum, optic nerve, kidney, skeletal muscle, and testis. Immunohistochemical study showed that ßB2, ßA1/A3 and γC -Crystallin were localized in M-line and I-band in skeletal muscle. ßB2 and γC -Crystallin were expressed in spermatocytes in testis. In addition, these crystallins were strongly expressed in the leading edges of cultured lens epithelial cells and co-localized with cytoskeletal protein actin.
Conclusions::
ßB2, ßA1/A3 and γC -Crystallins were abundantly expressed in non-lens tissues and co-localized with actin in the leading edge of migrating lens epithelial cells. Our studies suggested that ß and γ-Crystallins were related with changing of cell shape and cytoskeletal organization.
Keywords: crystallins • cytoskeleton • chaperones