Brian K. Rundall

Suberoylanilide Hydroxamic Acid Induces Akt-mediated Phosphorylation of p300, Which Promotes Acetylation and Transcriptional Activation of RelA/p65

We have previously demonstrated that the transcription factor NF-κB is activated by histone deacetylase inhibitors in a PI3K/Akt-dependent manner. The molecular mechanisms governing this process have not been well described. By virtue of their inhibitory action, it is unclear whether the addition of histone deacetylase inhibitors simply preserves the acetylation status of RelA/p65 or whether they actively stimulate signaling cascades that result in increased acetylation and transcription of NF-κB. Here we provide evidence that suberoylanilide hydroxamic acid stimulates NF-κB transcription through a signaling cascade that involves activation of both the serine/threonine kinase Akt and the p300 acetyltransferase. Using newly developed phosphospecific antibodies to p300 (pSer1834), and site-directed mutant proteins, we find that suberoylanilide hydroxamic acid stimulates Akt activity, which is required to phosphorylate p300 at Ser1834. Akt-mediated phosphorylation of p300 dramatically increases its acetyltransferase activity as measured by an increased acetylation of RelA/p65 at Lys310, a modification that is required for full NF-κB transcription. Importantly, coordinate activation of Akt/p300 pathway by suberoylanilide hydroxamic acid occurs at the chromatin level, resulting in recruitment of activated Akt (pSer473), p300 (pSer1834), acetylated RelA/p65 (Lys310), and RNA polymerase II to the NF-κB-dependent cIAP-2 and Bfl-1/A1 promoters. These studies provide evidence that histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid, not only inhibit deacetylase activity but also stimulate active NF-κB transcription and cell survival through signaling pathways involving Akt and increased p300 acetyltransferase activity.

Laparoscopic gastric bypass complicated by gastric pouch necrosis: considerations in gastroesophageal reconstruction.

Gastric pouch necrosis and intraabdominal sepsis is an uncommon complication following laparoscopic gastric bypass. The intraoperative management of this complication centers on resection of the necrotic pouch, esophageal diversion, drainage, and enteral access for nutrition. Reestablishing gastrointestinal continuity at a later surgery following this complication can be challenging. We present a case in which the colon was found to be unacceptable for use in reconstruction; the remaining stomach was used as the conduit for a transhiatal reconstruction of gastrointestinal continuity instead.