The adenovirus type 2/5 E1A proteins transform primary baby rat kidney (BRK) cells in cooperation with the activated Ras (T24 ras) oncoprotein. The N-terminal half of E1A (exon 1) is essential for this transformation activity. While the C-terminal half of E1A (exon 2) is dispensable, a region located between residues 225 and 238 of the 243R E1A protein negatively modulates in vitro T24 ras cooperative transformation as well as the tumorigenic potential of E1A/T24 ras-transformed cells. The same C-terminal domain is also required for binding of a cellular 48-kDa phosphoprotein, C-terminal binding protein (CtBP). We have cloned the cDNA for CtBP via yeast two-hybrid interaction cloning. The cDNA encodes a 439-amino acid (48 kDa) protein that specifically interacts with exon 2 in yeast two-hybrid, in vitro protein binding, and in vivo coimmunoprecipitation analyses. This protein requires residues 225-238 of the 243R E1A protein for interaction. The predicted protein sequence of the isolated cDNA is identical to amino acid sequences obtained from peptides prepared from biochemically purified CtBP. Fine mapping of the CtBP-binding domain revealed that a 6-amino acid motif highly conserved among the E1A proteins of various human and animal adenoviruses is required for this interaction. These results suggest that interaction of CtBP with the E1A proteins may play a critical role in adenovirus replication and oncogenic transformation.

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Adiponectin has recently been reported to generate a negative energy balance by increasing energy expenditure. However, it is unclear whether such effects require the presence and direct action of the adiponectin protein in the central nervous system. In this study, neither radiolabeled nonglycosylated nor glycosylated globular adiponectin crossed the blood-brain barrier (BBB) in mice. In addition, adiponectin was not detectable in human cerebrospinal fluid using various established methods. Using murine cerebral microvessels, we demonstrated expression of adiponectin receptors, which are upregulated during fasting, in brain endothelium. Interestingly, treatment with adiponectin reduced secretion of the centrally active interleukin-6 from brain endothelial cells, a phenomenon that was paralleled by a similar trend of other proinflammatory cytokines. In summary, our data suggest that direct effects of endogenous adiponectin on central nervous system pathways are unlikely to exist. However, the identification of adiponectin receptors on brain endothelial cells and the finding of a modified secretion pattern of centrally active substances from BBB cells provides an alternate explanation as to how adiponectin may evoke effects on energy metabolism. Diabetes 55: [141][142][143][144][145][146][147] 2006 A diponectin is an adipocyte-specific protein, and its structure consists of an NH 2 -terminal collagenous domain and a COOH-terminal globular domain (1-6). Various studies have associated adiponectin with insulin sensitivity (7-10). In epidemiological studies, high levels of adiponectin were associated with a reduced diabetes and coronary heart disease risk (11-13).A growing body of evidence suggests that adiponectin directly affects energy balance by increasing thermogenesis (14). Recent studies in C57BL6 mice demonstrated that globular and full-length adiponectin decreases body weight after central or peripheral administration by increasing energy expenditure. Comparable effects were observed in leptin-deficient ob/ob mice, while central treatment had no effects in agouti yellow mice (A y /a), suggesting melanocortin but not leptin receptor activation as an essential prerequisite for adiponectin-induced weight loss (15). In another study, however, peripheral administration of full-length adiponectin in A y /a mice increased energy expenditure, while central application was again without effect (16). Increased energy expenditure in adiponectintreated mice therefore might in part be mediated via peripheral adiponectin receptors, including those located at the luminal surface of the blood-brain barrier (BBB).However, systemic adiponectin levels increase after weight reduction, while that physiological state is clearly associated with reduced energy expenditure (17-19). Thus, the energy expenditure-increasing effects of adiponectin seem unlikely to play a major physiological role. The picture becomes even more confusing since the latest results indicate that mice with increased circulating adiponectin levels due to e...