Apoptosis plays a crucial role in mammalian development and complex control mechanisms exist to regulate these signaling pathways. Aberrant apoptosis of the salivary glands is induced by secondary side effects of head and neck irradiation, chemotherapeutics, or Sjogren's syndrome. p53 is an important regulator of apoptosis induced by DNA damage. The identification of two p53 homologues, p73 and p63, along with the selective activation of apoptotic target genes by these different homologues have added additional complexity in the understanding of how the decision to undergo apoptosis is executed. Increased expression of the p53 responsive genes bax and Fas has been shown in the lacrimal and salivary glands of Sjogren's syndrome patients and p53 is hypothesized to be associated in the pathogenesis of autoimmune disorders. The general goal of this proposal is to understand the induction of the p53 responsive genes in salivary acinar cells and regulation of this activity by the pro-survival serine/threonine protein kinase Akt. Specifically, the role Akt serves in suppressing apoptosis following DNA damage and the interaction with the p53 family of proteins will be examined. We hypothesize that Akt suppresses DNA damage induced apoptosis through a modulation of the p53 family of transcription factors.
Specific Aim 1 will define the in vivo mechanisms by which Akt suppresses gamma-irradiation-induced apoptosis in the salivary gland.
Specific Aim 2 will identify the requirement for p53 transcriptional activation in gamma-irradiation-induced salivary gland apoptosis.
Specific Aim 3 will examine the induction of p73 activity in salivary acinar cells and the effect of its suppression by activated Akt.
Specific Aim 4 will investigate the functions of p63 in salivary acinar cells and the ability of Akt to regulate these functions. Transiently cultured primary submandibular or parotid acinar cells isolated from mice provide a unique environment to examine the regulation of apoptosis. In addition, a transgenic mouse strain that expresses activated Akt has been used as a novel reagent in understanding the suppression of apoptosis induced by a variety of stimuli in salivary acinar cells. New understanding of the fundamental biological process of p53 regulation could have a powerful impact on clinical therapeutics for salivary glands.
