Co-culturing experiments reveal the uptake of myo-inositol phosphate synthase (EC 5.5.1.4) in an inositol auxotroph of Saccharomyces cerevisiae.

BACKGROUND: Myo-Inositol Phosphate Synthase (MIP) catalyzes the conversion of glucose 6- phosphate into inositol phosphate, an essential nutrient and cell signaling molecule. Data obtained, first in bovine brain and later in plants, established MIP expression in organelles and in extracellular environments. A physiological role for secreted MIP has remained elusive since its first detection in intercellular space. To provide further insight into the role of MIP in intercellular milieus, we tested the hypothesis that MIP may function as a growth factor, synthesizing inositol phosphate in intercellular locations requiring, but lacking ability to produce or transport adequate quantities of the cell-cell communicator. This idea was experimentally challenged, utilizing a Saccharomyces cerevisiae inositol auxotroph with no MIP enzyme, permeable membranes with a 0.4 µm pore size, and cellular supernatants as external sources of inositol isolated from S. cerevisiae cells containing either wild-type enzyme (Wt-MIP), no MIP enzyme, auxotroph (Aux), or a green fluorescent protein (GFP) tagged reporter enzyme (MIP- GFP) in co- culturing experiments. RESULTS: Resulting cell densities and microscopic studies with corroborating biochemical and molecular analyses, documented sustained growth of Aux cells in cellular supernatant, concomitant with the uptakeof MIP, detected as MIP-GFP reporter enzyme. These findings revealed previously unknown functions, suggesting that the enzyme can: (1) move into and out of intercellular space, (2) traverse cell walls, and (3) act as a growth factor to promote cellular proliferation of an inositol requiring cell. CONCLUSIONS: Co-culturing experiments, designed to test a probable function for MIP secreted in extracellular vesicles, uncovered previously unknown functions for the enzyme and advanced current knowledge concerning spatial control of inositol phosphate biosynthesis. Most importantly, resulting data identified an extracellular vesicle (a non-viral vector) that is capable of synthesizing and transporting inositol phosphate, a biological activity that can be used to enhance specificity of current inositol phosphate therapeutics.

Development of a Tool to Assess Trainees' Ability to Design and Conduct Quality Improvement Projects.

An important competency for residents developing skills in quality improvement (QI) and patient safety (PS) is to independently carry out an improvement project. The authors describe the development and reliability testing of the Quality Improvement Project Evaluation Rubric (QIPER) for use in rating project presentations in the Department of Veterans Affairs Chief Resident in Quality and Safety Program. QIPER contains 19 items across 6 domains to assess competence in designing, implementing, analyzing results of, and reporting on a QI/PS project. Interrater reliability of the instrument was calculated using the intraclass correlation coefficient (ICC). QIPER scores ranged from 28 to 72 out of a possible 76. QIPER demonstrated good reliability overall (ICC = 0.63). Although further testing is warranted, QIPER shows promise as a tool to assess a comprehensive set of skills involved in conducting QI/PS projects and has the sensitivity to detect varied competence and utility for providing learner feedback.