A novel, non-canonical mechanism of regulation of MST3 (mammalian Sterile20-related kinase 3)

The canonical pathway of regulation of the germinal centre kinase (GCK) III subgroup member, mammalian Sterile20-related kinase 3 (MST3), involves a caspase-mediated cleavage between N-terminal catalytic and C-terminal regulatory domains with possible concurrent autophosphorylation of the activation loop MST3(Thr178-), induction of Ser-/Thr-protein kinase activity and nuclear localisation. We identified an alternative ‘non-canonical’ pathway of MST3 activation (regulated primarily through dephosphorylation) which may also be applicable to other GCKIII (and GCKVI) subgroup members. In the basal state, inactive MST3 co-immunoprecipitated with the Golgi protein, GOLGA2/gm130. Activation of MST3 by calyculin A (a protein Ser-/Thr- phosphatase 1/2A inhibitor) stimulated (auto)phosphorylation of MST3(Thr178-) in the catalytic domain with essentially simultaneous cis-autophosphorylation of MST3(Thr328-) in the regulatory domain, an event also requiring the MST3(341-376) sequence which acts as a putative docking domain. MST3(Thr178-) phosphorylation increased MST3 kinase activity but this activity was independent of MST3(Thr328-) phosphorylation. Interestingly, MST3(Thr328-) lies immediately C-terminal to a STRAD pseudokinase-like site recently identified as being involved in binding of GCKIII/GCKVI members to MO25 scaffolding proteins. MST3(Thr178- /Thr328-) phosphorylation was concurrent with dissociation of MST3 from GOLGA2/gm130 and association of MST3 with MO25, and MST3(Thr328-) phosphorylation was necessary for formation of the activated MST3-MO25 holocomplex

Intracellular Trafficking and Synaptic Function of APL-1 in Caenorhabditis elegans

Background: Alzheimer’s disease (AD) is a neurodegenerative disorder primarily characterized by the deposition of b-amyloid plaques in the brain. Plaques are composed of the amyloid-b peptide derived from cleavage of the amyloid precursor protein (APP). Mutations in APP lead to the development of Familial Alzheimer’s Disease (FAD), however, the normal function of this protein has proven elusive. The organism Caenorhabditis elegans is an attractive model as the amyloid precursor-like protein (APL-1) is the single ortholog of APP, and loss of apl-1 leads to a severe molting defect and early larval lethality. Methodology/Principal Findings: We report here that lethality and molting can be rescued by full length APL-1, C-terminal mutations as well as a C-terminal truncation, suggesting that the extracellular region of the protein is essential for viability. RNAi knock-down of apl-1 followed by drug testing on the acetylcholinesterase inhibitor aldicarb showed that loss of apl-1 leads to aldicarb hypersensitivity, indicating a defect in synaptic function. The aldicarb hypersensitivity can be rescued by full length APL-1 in a dose dependent fashion. At the cellular level, kinesins UNC-104/KIF-1A and UNC-116/kinesin-1 are positive regulators of APL-1 expression in the neurons. Knock-down of the small GTPase rab-5 also leads to a dramatic decrease in the amount of apl-1 expression in neurons, suggesting that trafficking from the plasma membrane to the early endosome is important for apl-1 function. Loss of function of a different small GTPase, UNC-108, on the contrary, leads t

Structural Comparison of Human Mammalian Ste20-Like Kinases

BACKGROUND: The serine/threonine mammalian Ste-20 like kinases (MSTs) are key regulators of apoptosis, cellular proliferation as well as polarization. Deregulation of MSTs has been associated with disease progression in prostate and colorectal cancer. The four human MSTs are regulated differently by C-terminal regions flanking the catalytic domains. PRINCIPAL FINDINGS: We have determined the crystal structure of kinase domain of MST4 in complex with an ATP-mimetic inhibitor. This is the first structure of an inactive conformation of a member of the MST kinase family. Comparison with active structures of MST3 and MST1 revealed a dimeric association of MST4 suggesting an activation loop exchanged mechanism of MST4 auto-activation. Together with a homology model of MST2 we provide a comparative analysis of the kinase domains for all four members of the human MST family. SIGNIFICANCE: The comparative analysis identified new structural features in the MST ATP binding pocket and has also defined the mechanism for autophosphorylation. Both structural features may be further explored for inhibitors design. ENHANCED VERSION: This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1

Radiologisch-medizinische Desktop-Konferenzen - Klinische Evaluation des Teleradiologiesystems KAMEDIN im Routinebetrieb eines radiologischen Instituts

KAMEDIN ist ein Teleradiologieprojekt der Deutschen Telekom, welches ueber ISDN-Verbindungen den Transfer, die Visualisierung und die Online-Praesentation digitaler radiologischer Bilddaten ermoeglicht. Im Rahmen eines Feldversuches wurde die Anwendbarkeit des KAMEDIN-Systems im klinischen Routinebetrieb getestet und eine Anpassung der Software an die radiologische bildgebung vorgenommen. In einem Zeitraum von sechs Monaten wurden ueber 50 Telekonferenzen mit durchschnittlich 36 CT-Bildern pro Patient uebertragen. Die Vorbereitungszeit pro Patient betrug im Mittel 10 Minuten, die Uebertragungszeit 2 Minuten, und die Konferenzzeit 8 Minuten. Auftretende Softwareprobleme wurden analysiert und Loesungsprobleme erarbeitet. KAMEDIN kann durch eine weitere Anpassung den Erfordernissen der Telekommunikation in einer rdiologischen Abteilung gerecht werden