A major cause of ocular morbidity in the United States is lacrimal insufficiency, which affects 10 million Americans, primarily women. Approximately one fifth of these cases are clearly autoimmune-mediated and accompanied by additional symptoms which lead to the diagnosis of Sjogren's syndrome. The remainder of cases, designated as Non-Sjogren's lacrimal insufficiency, may also be mediated by the immune system. In the lacrimal gland, defects in membrane trafficking including altered processing of internalized and newly synthesized constituents through the endocytic and secretory pathways have been proposed to contribute to the development of dry eye and the autoimmune disease Sjogren s syndrome. Despite the hypothesis that defective trafficking plays a role in production of autoantigens in the lacrimal gland, little is known about the precise mechanisms by which altered trafficking patterns might occur. In interphase cells, microtubules provide a network which supports the movement of membranes driven by two different cytoplasmic motor proteins, kinesin and cytoplasmic dynein. Despite their importance in membrane trafficking, little is known about the involvement of these motors in normal and defective trafficking in the lacrimal gland. The PI has explored the membrane association and in vitro properties of kinesin from lacrimal acinar cells. Preliminary data suggest that kinesin plays a role in secretion under conditions that represent normal function and also under conditions in which traffic has been altered by sustained stimulation. Since such conditions may underlie the initiation of local autoimmune responses that may progress to Sjogren's syndrome or non-Sjogren's lacrimal insufficiency, these findings necessitate a more comprehensive investigation of the role of microtubule-based transport and specifically, kinesin, in lacrimal acinar membrane trafficking. The focus of this proposal is therefore: a. To identify the changes in lacrimal acinar membrane trafficking caused by disruption of microtuble-based motility. b. To define the biochemical properties and membrane interactions of kinesin isolated from lacrimal acinar cells. c. To determine whether stimulation of lacrimal secretion by carbachol, a secretagogue acting through diacylglycerol and Ca2+ -dependent pathways, alters kinesin activity. Once the function of kinesin is defined in resting and stimulated cells from normal rabbits, the PI may begin to question whether kinesin activity is altered in isolated acini from a recently described rabbit model of autoimmune dacryadenitis which exhibits features of Sjogren's syndrome.
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