The Mitochondrial Hsp90 TRAP1 and Alzheimer's Disease

Alzheimer’s Disease (AD) is the most common form of dementia, characterised by intra- and extracellular protein aggregation. In AD, the cellular protein quality control (PQC) system is derailed and fails to prevent the formation of these aggregates. Especially the mitochondrial paralogue of the conserved Hsp90 chaperone class, tumour necrosis factor receptor-associated protein 1 (TRAP1), is strongly downregulated in AD, more than other major PQC factors. Here, we review molecular mechanism and cellular function of TRAP1 and subsequently discuss possible links to AD. TRAP1 is an interesting paradigm for the Hsp90 family, as it chaperones proteins with vital cellular function, despite not being regulated by any of the co-chaperones that drive its cytosolic paralogues. TRAP1 encloses late folding intermediates in a non-active state. Thereby, it is involved in the assembly of the electron transport chain, and it favours the switch from oxidative phosphorylation to glycolysis. Another key function is that it ensures mitochondrial integrity by regulating the mitochondrial pore opening through Cyclophilin D. While it is still unclear whether TRAP1 itself is a driver or a passenger in AD, it might be a guide to identify key factors initiating neurodegeneration.

Secondary coloperineal pull-through and double dynamic graciloplasty after Miles resection--feasible, but with a high morbidity

PURPOSE

Until recently, patients who underwent abdominoperineal resections had to cope with a colostomy for the rest of their lives. For some of these patients this colostomy was a terrible burden, physically and mentally. Publications about abdominoperineal pull-through and double dynamic graciloplasty immediately after a Miles resection showed good results. The purpose of this study was to investigate the procedure as a secondary approach after abdominoperineal resections.

METHODS

In this study seven patients were evaluated. All had had an abdominoperineal resection and proved to have unbearable problems with their stoma. All had a secondary pull-through and double dynamic graciloplasty, a mean of 8.5 (range, 1.1-34.8) years after the Miles resection.

RESULTS

In five patients continence was regained; two were reversed to colostomy because of several complications. Patients who had a successful outcome also suffered from numerous complications, with a total mean hospital stay of 73.8 (range, 27-167) days, a mean of 3.1 (range, 1-6) additional operations, and 1.8 (range, 0-4) readmissions.

CONCLUSION

Secondary anorectal reconstruction after abdominoperineal resection is a feasible option, but with a high morbidity. Because of this the procedure was stopped at the beginning of 1997.