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Mammalian small heat-shock proteins (sHSPs) are molecular chaperones that form polydisperse and dynamic complexes with target proteins, serving as a first line of defense in preventing their aggregation into either amorphous deposits or amyloid fibrils. Their apparently broad target specificity makes sHSPs attractive for investigating ways to tackle disorders of protein aggregation. The two most abundant sHSPs in human tissue are αB-crystallin (ABC) and HSP27; here we present high-resolution structures of their core domains (cABC, cHSP27), each in complex with a segment of their respective C-terminal regions. We find that both truncated proteins dimerize, and although this interface is labile in the case of cABC, in cHSP27 the dimer can be cross-linked by an intermonomer disulfide linkage. Using cHSP27 as a template, we have designed an equivalently locked cABC to enable us to investigate the functional role played by oligomerization, disordered N and C termini, subunit exchange, and variable dimer interfaces in ABC. We have assayed the ability of the different forms of ABC to prevent protein aggregation in vitro. Remarkably, we find that cABC has chaperone activity comparable to that of the full-length protein, even when monomer dissociation is restricted through disulfide linkage. Furthermore, cABC is a potent inhibitor of amyloid fibril formation and, by slowing the rate of its aggregation, effectively reduces the toxicity of amyloid-β peptide to cells. Overall we present a small chaperone unit together with its atomic coordinates that potentially enables the rational design of more effective chaperones and amyloid inhibitors.

Amyloid fibril formation by the extracellular protein β2-microglobulin (β2m) and its subsequent accumulation in periarticular tissues have been linked to dialysis-related amyloidosis. A natural variant of human β2m responsible for aggressive systemic amyloidosis contains an aspartate to asparagine mutation at residue 76 (i.e. D76N β2m), which readily forms amyloid fibrils in vitro under physiological conditions. In this study, we examined the role of the extracellular molecular chaperone clusterin in modulating D76N β2m fibril formation in vitro under physiological conditions. The presence of extrinsic charged amino acids modulated D76N β2m fibril formation, implying that electrostatic interactions are involved in the protein's aggregation. Thioflavin T (ThT) and 1-anilinonaphthalene-8-sulfonate fluorescence assays indicated that clusterin interacts via hydrophobic and electrostatic forces with the monomeric, prefibrillar and fibrillar species of D76N β2m. As a result, clusterin was incorporated into D76N β2m aggregates during the latter's fibril formation, as indicated by SDS-PAGE of depolymerised fibrils. SYPRO Orange and ThT fluorescence assays suggested that, compared to pure D76N β2m fibrils, those formed in the presence of clusterin are chemically more stable with a reduced ability to act as nucleation seeds. Detailed 15N NMR relaxation studies of mixtures of 15N-labelled β2m with clusterin confirmed that the chaperone interacts transiently and non-specifically with monomeric β2m. Clusterin inhibits both primary and secondary nucleation of D76N β2m fibril formation. In doing so, clusterin binds to D76N β2m fibrils and stabilises them to prevent possible fragmentation. In vivo , the multifaceted chaperone action of clusterin may delay, if not prevent, β2m amyloid proliferation and deposition in tissues. Accumulation of β2-microglobin in tissues is responsible for the disease dialysis-related amyloidosis. The D76N mutant is highly amyloidogenic. An in vitro biophysical and spectroscopic investigation of D76N β2-microglobin amyloid fibril formation and its inhibition by the common extracellular chaperone, clusterin, is described. In vivo , clusterin may play an important role in preventing β2-microglobin deposition. CH23082_TOC.jpg [ABSTRACT FROM AUTHOR]

The Veggie vegetable production system was launched to the International Space Station with three sets of test plants for an initial hardware validation test, designated VEG-01. VEG-01A and B featured the crop ‘Outredgeous’ red romaine lettuce, while VEG-01C tested ‘Profusion’ zinnia plants for longer duration growth and flowering characteristics. Irrigation of plants in all three growth studies presented a challenge, with lettuce suffering from inadequate water and zinnia suffering from excess water. Direct plant pillow watering by crew members enabled plant growth, and returned samples from the first crop, VEG-01A, indicated that food safety was acceptable. VEG-01B plants at harvest were split to allow for on-orbit crew consumption as well as science sample return. Direct-watered zinnias suffered fungal growth and other physiological stresses, but two plants survived and these produced numerous flowers. The VEG-01 series allowed a large amount of data on system performance, human factors, procedures, microbiology, and chemistry of space-grown plants to be gathered. Observations from these tests are helping to drive future hardware modifications and provide information on food crop growth and development in a microgravity environment.

The creator of the Policy Governance model explains a system whereby the superintendent/CEO is not responsible for governance. Under Policy Governance, the board is solely responsible for describing and fulfilling its own job (determining what the public purchases for the next generation), and the administrators run the schools. (MLH)

The Policy Governance model's philosophical foundations lie in Rousseau's social contract, Greenleaf's servant-leadership, and modern management theory. Policy Governance stresses primacy of the owner-representative role; full-board authority; superintendents as chief executive officers; authoritative prescription of "ends," bounded freedom for "means," and system-focused superintendent evaluation. (MLH)