An Ancient Duplication of Exon 5 in the Snap25 Gene Is Required for Complex Neuronal Development/Function

Alternative splicing is an evolutionary innovation to create functionally diverse proteins from a limited number of genes. SNAP-25 plays a central role in neuroexocytosis by bridging synaptic vesicles to the plasma membrane during regulated exocytosis. The SNAP-25 polypeptide is encoded by a single copy gene, but in higher vertebrates a duplication of exon 5 has resulted in two mutually exclusive splice variants, SNAP-25a and SNAP-25b. To address a potential physiological difference between the two SNAP-25 proteins, we generated gene targeted SNAP-25b deficient mouse mutants by replacing the SNAP-25b specific exon with a second SNAP-25a equivalent. Elimination of SNAP-25b expression resulted in developmental defects, spontaneous seizures, and impaired short-term synaptic plasticity. In adult mutants, morphological changes in hippocampus and drastically altered neuropeptide expression were accompanied by severe impairment of spatial learning. We conclude that the ancient exon duplication in the Snap25 gene provides additional SNAP-25-function required for complex neuronal processes in higher eukaryotes

Relationship between the Clinical Frailty Scale and short-term mortality in patients ≥ 80 years old acutely admitted to the ICU: a prospective cohort study.

BACKGROUND: The Clinical Frailty Scale (CFS) is frequently used to measure frailty in critically ill adults. There is wide variation in the approach to analysing the relationship between the CFS score and mortality after admission to the ICU. This study aimed to evaluate the influence of modelling approach on the association between the CFS score and short-term mortality and quantify the prognostic value of frailty in this context. METHODS: We analysed data from two multicentre prospective cohort studies which enrolled intensive care unit patients ≥ 80 years old in 26 countries. The primary outcome was mortality within 30-days from admission to the ICU. Logistic regression models for both ICU and 30-day mortality included the CFS score as either a categorical, continuous or dichotomous variable and were adjusted for patient's age, sex, reason for admission to the ICU, and admission Sequential Organ Failure Assessment score. RESULTS: The median age in the sample of 7487 consecutive patients was 84 years (IQR 81-87). The highest fraction of new prognostic information from frailty in the context of 30-day mortality was observed when the CFS score was treated as either a categorical variable using all original levels of frailty or a nonlinear continuous variable and was equal to 9% using these modelling approaches (p < 0.001). The relationship between the CFS score and mortality was nonlinear (p < 0.01). CONCLUSION: Knowledge about a patient's frailty status adds a substantial amount of new prognostic information at the moment of admission to the ICU. Arbitrary simplification of the CFS score into fewer groups than originally intended leads to a loss of information and should be avoided. Trial registration NCT03134807 (VIP1), NCT03370692 (VIP2)

Is the Swedish onshore bedrock suitable for carbon dioxidesequestration?

ISBN för värdpublikation: 978-91-987833-0-8</p

Carbon Capture and Storage (CCS) – the potential for mineral carbonation in the Swedish onshore bedrock

ISBN för värdpublikation: 978-9935-25-178-7</p

DARPP-32 and inhibitor-1 are expressed in pancreatic β-cells

Insulin secretion from pancreatic β-cells has to be tightly regulated to ensure accurate glucose homeostasis. The capacity of β-cells to respond to extracellular stimulation is determined by several signaling pathways. One important feature of these pathways is phosphorylation and subsequent dephosphorylation of a wide range of cellular substrates. Protein phosphatase 1 (PP1) is a major eukaryotic serine/threonine protein phosphatase that controls a multitude of physiological processes. We have investigated the expression and cellular distribution of two endogenous inhibitors of PP1 activity in β-cells. RT-PCR, Western blotting, and immunohistochemistry showed that DARPP-32 and inhibitor-1 are present in insulin-secreting endocrine β-cells. Subcellular fractionation of mouse islets revealed that both PP1 inhibitors predominantly localized to cytosol-enriched fractions. Inhibitor-1 was also present in fractions containing plasma membrane-associated proteins. These data indicate a potential role for DARPP-32 and inhibitor-1 in the regulation of PP1 activity in pancreatic β-cell stimulus-secretion coupling

Mint1, a Munc-18-interacting protein, is expressed in insulin-secreting β-cells

Munc-18-interacting (Mint) proteins are adaptors involved in regulation of synaptic vesicle exocytosis. We have investigated expression and cellular localization of Mint1 in pancreatic islets with special reference to insulin-secreting β-cells. Western blotting showed that Mint1 was expressed in hamster (HIT-T15) and rat (RINm5F) β-cell lines. Mint1 immunoreactivity was preferentially localized to the periphery of individual islet cells. RT-PCR analysis revealed that apart from Mint1, RINm5F cells and rat islets also transcribed the mRNAs for Mint2 and Mint3. Expression of Mint proteins in pancreatic β-cells suggests a functional role for these proteins in insulin granule exocytosis

Disabling Gbetagamma-SNAP-25 Interaction in Gene-Targeted Mice Results in Enhancement of Long-Term Potentiation at Schaffer Collateral-CA1 Synapses in the Hippocampus

Three SNARE proteins, SNAP-25, syntaxin 1A, and VAMP2 or synaptobrevin 2, constitute the minimal functional machinery needed for the regulated secretion of neurotransmitters. Dynamic changes in the regulated release of neurotransmitters are associated with the induction of long-term plasticity at central synapses. In-vitro studies have validated the C-terminus of SNAP-25 as a target for inhibitory Gi/o-coupled G-protein coupled receptors at a number of synapses. The physiological consequences of the interaction between Gi/o proteins and SNAP-25 in the context of activity-dependent long-term synaptic plasticity are not well understood. Here, we report direct ex-vivo evidence of the involvement of the C-terminus of SNAP-25 in inducing long-term potentiation of synaptic strength at Schaffer collateral-CA1 synapses using a gene-targeted mouse model with truncated C-terminus (carboxyl terminus) of SNAP-25. It has been shown previously that truncation of the three extreme C-terminal residues in SNAP-25[INCREMENT]3 homozygote mice reduces its interaction with the inhibitory Gbetagamma subunits two-fold. In in-vitro hippocampal slices, we show that these SNAP-25[INCREMENT]3 mice express significantly larger magnitude of long-term potentiation at hippocampal Schaffer collateral-CA1 synapses

Cyclin-Dependent Kinase 5 and Insulin Secretion

Cyclin-dependent kinase 5 (Cdk5) is emerging as a multifunctional kinase involved in regulating numerous cellular processes. Lately, Cdk5 has also emerged as a key controller of regulated membrane fusion in secretory cells. The pancreatic β-cell is highly specialized to secrete insulin in response to elevated glucose concentrations in the blood. The final biochemical events leading to insulin release from the β-cell are governed by a secretion apparatus that is similar to the presynaptic machinery mediating synaptic transmission in neuronal networks. We now summarize recent developments in the field of Cdk5 and regulated exocytosis and also present some novel findings regarding Cdk5’s effect on insulin secretion