Heterotrimeric guanine nucleotide binding (G) proteins composed of individual alpha, Beta and gamma subunits plays pivotal roles in the cellular physiology. It has recently been shown that pertussis toxin sensitive G-proteins, particularly the Gai-2 isoform, have a key role in number of growth pathways as well as in development. Recently mutations converting Gai-3 to an oncogene have been found in a number of tumors of endocrine origin. Wilms' tumor accounts for almost all childhood renal neoplasms. In a subset of this tumor as well as in individuals with Denys-Drash syndrome whose phenotype also includes male pseudohermaphroditism and glomerulosclerosis, mutations disable a transcription factor, WTI which is presumed to play a role in normal renal mitogenic and differentiating pathways. Although WTI has a known DNA binding sequence CGCCCCCGC, its target genes in renal cells have not been identified. In this proposal we provide evidence that Gai-2 subunit protooncogene is a target gene as its 5' flank contains a regulatory region in which Egr-l binding enhances gene transcription and WTI repress it. Also i this short DNA regulatory segment, a """"""""CCAAT"""""""" box participates in a negative feedback pathway for adenylyl cyclase where increased cAMP production increases gene transcription for the inhibitory Gai-2 subunit. The long term goal of this proposal is to understand the role and regulation of Gai-2 renal epithelial cell growth and development.
The specific aims i nclude (1) clarifying the role of Gai-2 in renal cell growth as well as the mechanism of inducing this effect, (2) sorting out the respective roles of Egr-1 and its competitive respessor WT-1 in the regulation of Gai-2 gene expression in renal cells and (3) investigating the cAMP inducible """"""""CCAAT"""""""" factors an how they interact with WT1 and Egr-1. These studies are likely to provide new insights into growth pathways contributory to the induction of Wilms' tumor and glomerulosclerosis. Furthermore, as Gai-2 is likely to regulate cell division and growth, we should gain insight into the processes by which the kidney responds to injury and hypertrophy.
| Kinane, T B; Komatsuzaki, K; Aleixo, M D et al. (1999) Regulation of the G protein Galphai2 by growth and development in fetal airway epithelium. Am J Respir Cell Mol Biol 20:35-42 |
| Kinane, T B; Kang, I; Chu, A et al. (1997) G alpha(i-2) mediates renal LLC-PK1 growth by a Raf-independent activation of p42/p44 MAP kinase. Am J Physiol 272:F273-82 |
| Burton, M D; Kawashima, A; Brayer, J A et al. (1997) RET proto-oncogene is important for the development of respiratory CO2 sensitivity. J Auton Nerv Syst 63:137-43 |
| Kinane, T B; Finder, J D; Kawashima, A et al. (1994) Growth of LLC-PK1 renal cells is mediated by EGR-1 up-regulation of G protein alpha i-2 protooncogene transcription. J Biol Chem 269:27503-9 |
