Regulation of intracellular phosphatidylinositol-4-phosphate by the Sac1 lipid phosphatase.

Phosphatidylinositol 4-phosphate (PtdIns(4)P) regulates diverse cellular processes, such as actin cytoskeletal organization, Golgi trafficking and vacuolar biogenesis. Synthesis and turnover of PtdIns(4)P is mediated by a set of specific lipid kinases and phosphatases. Here we show that the polyphosphoinositide phosphatase Sac1p has a central role in compartment-specific regulation of PtdIns(4)P. We have found that sac1Delta mutants show pleiotropic, synthetically lethal interactions with mutations in genes required for vacuolar protein sorting (Vps). Disruption of the SAC1 gene also caused a defect in the late endocytic pathway. These trafficking phenotypes correlated with a dramatic accumulation of PtdIns(4)P at vacuolar membranes. In addition, sac1 mutants displayed elevated endoplasmic reticulum PtdIns(4)P. The accumulation of PtdIns(4)P at the endoplasmic reticulum and vacuole and the endocytic defect could be compensated by mutations in the PtdIns 4-kinase Stt4p. Our results indicate that elimination of Sac1p causes accumulation of a Stt4p-specific PtdIns(4)P pool at internal membranes which impairs late endocytic and vacuolar trafficking. We conclude that Sac1p functions in confining PtdIns(4)P-dependent processes to specific intracellular membranes.

Role for lipid signaling and the cell integrity MAP kinase cascade in yeast septum biogenesis.

Polarized deposition of chitin at the bud neck is essential for cell separation in yeast. Chitin septum biogenesis is catalyzed by two distinct chitin synthase activities encoded by the CHS2 and CHS3 genes. The phosphoinositide phosphatase Sac1p is required for proper trafficking of the Chs3p chitin synthase. sac1 mutants also display a severe synthetic growth defect, with mutations in the SLT2 gene which encodes a MAP kinase involved in cell integrity. We characterized the defect that underlies this genetic interaction and found that sac1 Delta slt2 Delta cells arrest as large-budded cells because they fail to separate at the end of mitosis. This inability to complete cell division appears to be caused by an increased deposition of chitin at the septum area and correlates with a mislocalized accumulation of the Chs2p chitin synthase at the cell periphery. Our data therefore indicate that Sac1p and Slt2p have synergistic roles in regulating chitin septum biogenesis.

Surgery and adjuvant therapy in patients with diffuse peritonitis: cost analysis.

In a prospective, randomized, controlled trial the effect of high dose intravenous antithrombin III and intraabdominal donor serum was analyzed in 36 patients with diffuse secondary peritonitis. The direct cost for treatment was 25,370 euros per patient, and the post acute hospital care costs and societal costs were 6273 euros. The cost for intensive care of these patients accounted for approximately 83% of the direct costs, while the expenditures for operating theater and general wards accounted for 9% each. The most expensive factors were staff, medication, and blood products. The hospital incurred a deficit of 3696 euros for each patient after reimbursement from public health insurance companies. Quality of life as assessed by the gastrointestinal quality of life index (GIQI) showed a good outcome. On average 11 quality adjusted life years (QALY) were achieved. The cost per QALY was 2631 euros. Use of adjuvant therapy was associated with a reduced duration of intensive care unit (ICU) treatment, times on mechanical respiration, and hemofiltration; the cost of treatment was reduced by 6614 euros per patient. The additional cost of antithrombin III (5155 euros) was more than offset by the savings made when adjuvant therapy was used.