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R.K. Gangalum, S.P. Bhat; Significant Association of B–Crystallin With the Golgi in the Ocular Lens . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3872.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have recently shown that αB–crystallin (αB), a member of the small heat shock family of proteins is associated with the Golgi in a cell–cycle dependent fashion; following disassembly during mitosis and reassembly at the end of cell division and cytokinesis in U373 Glioblastoma cells(JBC 279:43374,2004). Other investigations have indicated that αB may have a role in the regulation of cellular growth. The ocular lens, with an epithelium that contains cells in various stages of cell division and differentiation, presents a useful paradigm for ascertaining the status of αB and its association with the perinuclear Golgi, in the context of cellular growth and differentiation. Methods: We used discontinuous sucrose density gradients coupled with immunoblotting to characterize association of αB with the Golgi in the postnuclear supernatants of day 10 and day 20 postnatal rat lenses. We examined primary cultures (derived from the lens epithelia of the rat and adult bovine lenses) and native lenses by confocal microscopy using Golgi–specific antiGM130 and antiαB. Results: A significant portion of αB is associated with Golgi membrane fractions in the postnuclear homogenates of the postnatal rat lenses. Both in the primary cultures of the rat lens as well as the primary cultures of the bovine lenses αB is predominantly associated with the perinuclear Golgi. This picture however changes when cells, which are elongated (presumably fiber cells in their early differentiation stages) are examined. In these cells the Golgi envelopes the nucleus and/or breaks into vesicles. Interestingly, examination of the native epithelium and the fiber cells in the lenses suggests that αB associates with the Golgi prominently in the dividing and the differentiating zone and then follows elongation of the nucleus in the terminally differentiating fiber cells. Conclusions: The presence of αB–crystallin in the Golgi in lens epithelium is dictated by the status of the cell in the cell cycle. While cultured cells shows perfect perinuclear colocalization of the αB and GM130 in the perinuclear area, the native lens epithelial cells and the fiber cells shows various structures of the Golgi and differential association of αB with it. This association is seen increasingly in the dividing and the differentiating epithelium/fiber cells suggesting an important role for αB–crystallin via its association with the Golgi, in cellular differentiation in the ocular lens.
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