Effect of overexpression of constitutively active PKCalpha on rat lacrimal gland protein secretion.

PURPOSE The lacrimal gland secretes water, electrolytes, and protein into the tear film. Decreased secretion from the lacrimal gland can lead to dry eye syndromes with deleterious effects on vision. Protein kinase C (PKC)-alpha plays a major role in cholinergic- and alpha1-adrenergic-induced protein secretion from the lacrimal gland. This study was undertaken to determine whether activation of PKCalpha alone would induce lacrimal gland protein secretion by examining the effects of overexpression of constitutively active PKCalpha. METHODS Rat lacrimal gland acini were transduced with an adenovirus containing a gene for constitutively active PKCalpha. Protein secretion was measured in response to cholinergic and alpha1-adrenergic agonist stimulation. RESULTS More than 84% of acinar cells were transduced, and PKCalpha expression was increased 176-fold. Western blot analysis using an antibody to phosphorylated (activated) PKCalpha indicated that the overexpressed PKCalpha was active, and basal secretion was increased. Cholinergic agonist-stimulated protein secretion was not stimulated above basal secretion, whereas alpha1-adrenergic-agonist-stimulated protein secretion was increased in transduced acini. CONCLUSIONS Basal lacrimal gland protein secretion can be stimulated by bypassing the release of neurotransmitters and activating PKCalpha, possibly leading to the development of new treatments for dry eye syndromes.