Impaired malin expression and interaction with partner proteins in Lafora disease.

Lafora disease (LD) is an autosomal recessive myoclonus epilepsy with onset in the teenage years leading to death within a decade of onset. LD is characterized by the overaccumulation of hyperphosphorylated, poorly branched, insoluble, glycogen-like polymers called Lafora bodies. The disease is caused by mutations in either EPM2A, encoding laforin, a dual specificity phosphatase that dephosphorylates glycogen, or EMP2B, encoding malin, an E3-ubiquitin ligase. While glycogen is a widely accepted laforin substrate, substrates for malin have been difficult to identify partly due to the lack of malin antibodies able to detect malin in vivo. Here we describe a mouse model in which the malin gene is modified at the C-terminus to contain the c-myc tag sequence, making an expression of malin-myc readily detectable. Mass spectrometry analyses of immunoprecipitates using c-myc tag antibodies demonstrate that malin interacts with laforin and several glycogen-metabolizing enzymes. To investigate the role of laforin in these interactions we analyzed two additional mouse models: malin-myc/laforin knockout and malin-myc/LaforinCS, where laforin was either absent or the catalytic Cys was genomically mutated to Ser, respectively. The interaction of malin with partner proteins requires laforin but is not dependent on its catalytic activity or the presence of glycogen. Overall, the results demonstrate that laforin and malin form a complex in vivo, which stabilizes malin and enhances interaction with partner proteins to facilitate normal glycogen metabolism. They also provide insights into the development of LD and the rescue of the disease by the catalytically inactive phosphatase.

What are the anticipated benefits, risks, barriers and facilitators to implementing person-centred outcome measures into routine care for children and young people with life-limiting and life-threatening conditions? A qualitative interview study with key stakeholders.

BACKGROUND: There is a growing evidence-base underpinning implementation of person-centred outcome measures into adult palliative care. However evidence on how best to achieve this with children facing life-threatening and life-limiting conditions is limited. AIM: To identify the anticipated benefits, risks, barriers and facilitators to implementing person-centred outcome measures for children with life-limiting and life-threatening conditions. DESIGN: Cross-sectional qualitative semi-structured interview study with key stakeholders analysed using Framework analysis informed by the adapted-Consolidated Framework for Implementation Research. SETTING/PARTICIPANTS: A total of n = 26 children with life-limiting or life-threatening conditions, n = 40 parents/carers, n = 13 siblings and n = 15 health and social care professionals recruited from six hospitals and three children's hospices and n = 12 Commissioners of health services. RESULTS: All participants were supportive of future implementation of person-centred outcome measures into care. Anticipated benefits included: better understanding of patient and family priorities, improved communication and collaborative working between professionals and families and standardisation in data collection and reporting. Anticipated risks included increased workload for staff and measures not being used as intended. Implementation barriers included: acceptability and usability of outcome measures by children; burden and capacity of parents/carers regarding completion; privacy concerns; and language barriers. Implementation facilitators included designing measures using language that is meaningful to children and families, ensuring potential benefits of person-centred outcome measures are communicated to encourage 'buy-in' and administering measures with known and trusted professional. CONCLUSIONS: Implementation of person-centred outcome measures offer potential benefits for children with life-limiting and life-threatening conditions. Eight recommendations are made to maximise benefits and minimise risks in implementation.

'My life is a mess but I cope': An analysis of the language children and young people use to describe their own life-limiting or life-threatening condition.

BACKGROUND: Children and young people with life-limiting and life-threatening conditions have multidimensional needs and heterogenous cognitive and communicative abilities. There is limited evidence to support clinicians to tailor their communication to each individual child. AIM: To explore the language children and young people use to describe their own condition, to inform strategies for discussing needs and priorities. DESIGN: Positioned within a social constructivist paradigm, a secondary discourse analysis of semi-structured interview data was conducted incorporating the discourse dynamics approach for figurative language. SETTING/PARTICIPANTS: A total of 26 children and young people aged 5-17 years with life-limiting or life-threatening conditions (6 cancer; 20 non-cancer) were recruited from nine clinical services (six hospitals and three hospices) across two UK nations. RESULTS: The language children and young people use positions them as 'experts in their condition'. They combine medical terminology with their preferred terms for their body to describe symptoms and treatments, and use comparatives and superlatives to communicate their health status. Their language depicts their condition as a 'series of (functional and social) losses', which single them out from their peers as 'the sick one'. Older children and young people also incorporate figurative language to expand their descriptions. CONCLUSION/DISCUSSION: Children and young people can provide rich descriptions of their condition. Paying attention to their lexical choices, and converging one's language towards theirs, may enable more child-centred discussions. Expanding discussions about 'what matters most' with consideration of the losses and differences they have experienced may facilitate a fuller assessment of their concerns, preferences and priorities.

Implementing brief and low-intensity psychological interventions for children and young people with internalizing disorders: a rapid realist review.

INTRODUCTION: Many children fail to receive the mental health treatments they need, despite strong evidence demonstrating efficacy of brief and low-intensity psychological interventions. This review identifies the barriers and facilitators to their implementation. SOURCES OF DATA: PsycInfo, EMBASE and Medline were searched and a systematic approach to data extraction using Normalization Process Theory highlighted key mechanisms and contextual factors. AREAS OF AGREEMENT: Ten interventions from 9 papers, including 371 young people, were included. Studies identified organizational demands, lack of implementation strategy and stigma as barriers to implementation, and clear training and plans for implementation as facilitators. AREAS OF CONTROVERSY: No standardized implementation outcomes were used across papers so meta-analysis was not possible. GROWING POINTS: Barriers and facilitators have been clearly identified across different settings. AREAS TIMELY FOR DEVELOPING RESEARCH: Longitudinal studies can identify methods and processes for enhancing long-term implementation and considers ways to monitor and evaluate uptake into routine practice.

Does the impact of bereavement vary between same and different gender partnerships? A representative national, cross-sectional study.

BACKGROUND: Data suggest poorer bereavement outcomes for lesbian, gay and bisexual people, but this has not been estimated in population-based research. This study compared bereavement outcomes for partners of same-gender and different-gender decedents. METHODS: In this population-based, cross-sectional survey of people bereaved of a civil partner or spouse 6-10 months previously, we used adjusted logistic and linear regression to investigate outcomes of interest: (1) positive screen on Inventory of Complicated Grief (ICG), (2) positive screen on General Health Questionnaire (GHQ), (3) grief intensity (ICG) and (4) psychiatric symptoms (GHQ-12). RESULTS: Among 233 same-gender partners and 329 of different-gender partners, 66.1% [95% confidence interval (CI) 60.0-72.2] and 59.2% [95% CI (53.9-64.6)] respectively screened positive for complicated grief on the ICG, whilst 76.0% [95% CI (70.5-81.5)] and 69.3% [95% CI (64.3-74.3)] respectively screened positive on the GHQ-12. Same-gender bereaved partners were not significantly more likely to screen positive for complicated grief than different-gender partners [adjusted odds ratio (aOR) 1.56, 95% CI (0.98-2.47)], p = 0.059, but same-gender bereaved partners were significantly more likely to screen for psychiatric caseness [aOR 1.67 (1.02, 2.71) p = 0.043]. We similarly found no significant association of partner gender with grief intensity [B = 1.86, 95% CI (-0.91to 4.63), p = 0.188], but significantly greater psychological distress for same-gender partners [B = 1.54, 95% CI (-0.69-2.40), p < 0.001]. CONCLUSIONS: Same-gender bereaved partners report significantly more psychological distress. In view of their poorer sub-clinical mental health, clinical and bereavement services should refine screening processes to identify those at risk of poor mental health outcomes.

LGBT+ partner bereavement and appraisal of the Acceptance-Disclosure Model of LGBT+ bereavement: A qualitative interview study.

BACKGROUND: Support from social networks is vital after the death of a partner. Lesbian, gay, bisexual and/or transgender (LGBT+) people can face disenfranchisement and isolation in bereavement. The Acceptance-Disclosure Model (of LGBT+ bereavement) posits that experiences are shaped by the extent to which individuals feel able to disclose their bereavement to others, and whether that loss is acknowledged appropriately. AIM: To explore LGBT+ specific experiences of partner bereavement; determine decision-making processes regarding disclosure of relationships/identities; and appraise the Acceptance-Disclosure Model using primary qualitative data. DESIGN: Exploratory in-depth qualitative interview study positioned within a social constructivist paradigm. Data were analysed using inductive and deductive reflexive thematic analysis. SETTING/PARTICIPANTS: 21 LGBT+ people from across England bereaved of their civil partner/spouse. RESULTS: Participants described LGBT+ specific stressors in bereavement: lack of recognition of their loss; inappropriate questioning; unwanted disclosure of gender history; and fears of discrimination when accessing support. Disclosure of LGBT+ identities varied across social networks. Some participants described hiding their identities and bereavement to preserve relationships, and challenging intersections between LGBT+ identities and other aspects of culture or self. These findings provide primary evidence to support the Acceptance-Disclosure Model. CONCLUSIONS: LGBT+ people face additional stressors in bereavement. Not all LGBT+ people want to talk directly about their relationships/identities. Sensitive exploration of support needs, aligned with preferences around disclosure of identities, can help foster trust. Five recommendations for inclusive practice are presented. Further research should consider whether the Acceptance-Disclosure Model has utility to explain bereavement experiences for other isolated or disenfranchised groups.

Spiritual, religious, and existential concerns of children and young people with life-limiting and life-threatening conditions: A qualitative interview study.

BACKGROUND: Despite being a core domain of palliative care, primary data on spiritual and existential concerns has rarely been collected among children with life-limiting and life-threatening conditions and their families. Existing evidence has tended to focus on the religious aspects among children with cancer. AIM: To identify the spiritual needs of children with life-limiting and life-threatening conditions. DESIGN: Cross-sectional semi-structured, qualitative interview study with children, families and health and social care professionals. Verbatim transcripts were analysed using Framework analysis. SETTING/PARTICIPANTS: Purposively sampled children with life-limiting and life-threatening conditions, their parents and siblings, health and social care professionals recruited from six hospitals and three children's hospices in the UK, and commissioners of paediatric palliative care services recruited through networks and a national charity. RESULTS: One hundred six participants were interviewed: 26 children (5-17 years), 53 family members (parents/carers of children 0-17 years and siblings (5-17 years)), 27 professionals (health and social care professionals and commissioners of paediatric palliative care). Themes included: living life to the fullest, meaning of life and leaving a legacy, uncertainty about the future, determination to survive, accepting or fighting the future and role of religion. Children as young as 5 years old identified needs or concerns in the spiritual domain of care. CONCLUSIONS: Addressing spiritual concerns is essential to providing child- and family-centred palliative care. Eliciting spiritual concerns may enable health and social care professionals to identify the things that can support and enhance a meaningful life and legacy for children and their families.

Achieving child-centred care for children and young people with life-limiting and life-threatening conditions-a qualitative interview study.

This study aims to identify the symptoms, concerns, and care priorities of children with life-limiting conditions and their families. A semi-structured qualitative interview study was conducted, seeking perspectives from multiple stakeholders on symptoms, other concerns, and care priorities of children and young people with life limiting and life-threatening conditions and their families. Participants were recruited from six hospitals and three children's hospices in the UK. Verbatim transcripts were analysed using framework analysis. A total of 106 participants were recruited: 26 children (5-17 years), 40 parents (of children 0-17 years), 13 siblings (5-17 years), 15 health and social care professionals, 12 commissioners. Participants described many inter-related symptoms, concerns, and care priorities impacting on all aspects of life. Burdensome symptoms included pain and seizures. Participants spoke of the emotional and social impacts of living with life-limiting conditions, such as being able to see friends, and accessing education and psychological support. Spiritual/existential concerns included the meaning of illness and planning for an uncertain future. Data revealed an overarching theme of pursuing 'normality', described as children's desire to undertake usual childhood activities. Parents need support with practical aspects of care to help realise this desire for normality. CONCLUSION: Children with life-limiting conditions and their families experience a wide range of inter-related symptoms, concerns, and care priorities. A holistic, child-centred approach to care is needed, allowing focus on pursuit of normal childhood activities. Improvements in accessibility, co-ordination, and availability of health services are required to achieve this. WHAT IS KNOWN: • Existing evidence regarding symptoms, concerns, and care priorities for children with life-limiting conditions is largely limited to proxy-reported data and those with a cancer diagnosis. • Child-centred care provision must be directed by children's perspectives on their priorities for care. WHAT IS NEW: • Social and educational activities are more important to children with life-limiting conditions than their medical concerns. • A holistic approach to care is required that extends beyond addressing medical needs, in order to support children with life-limiting conditions to focus on pursuit of normal childhood activities.

Reflective insights from developing a palliative care children and young people's advisory group.

BACKGROUND: The importance of actively involving patient and public members throughout the different stages of palliative care and health research projects is widely acknowledged, however patient and public involvement work rarely considers insight from children and young people. Although this is becoming increasingly recognised in other areas of research, there is currently no structured guidance on how to best involve children and young people in palliative care research. AIM: To plan and deliver a Young People's Advisory Group in palliative care and health research at a secondary school. FINDINGS: Attending an after-school 'Health and Social Research Methods Club' for 11 weeks benefitted children and researchers. Children were taught about data collection methods, data analysis and ethics in health research and used these skills to provide valuable feedback which has been implemented in current palliative care research projects. Children took part in considered discussions around palliative care topics and enjoyed attending the group. CONCLUSION: This project has equipped researchers with skills and provided a structured template for future Young People's Advisory Groups, ensuring the unique voices of children and young people are considered and valued in future palliative care research.

Lack of liver glycogen causes hepatic insulin resistance and steatosis in mice.

Disruption of the Gys2 gene encoding the liver isoform of glycogen synthase generates a mouse strain (LGSKO) that almost completely lacks hepatic glycogen, has impaired glucose disposal, and is pre-disposed to entering the fasted state. This study investigated how the lack of liver glycogen increases fat accumulation and the development of liver insulin resistance. Insulin signaling in LGSKO mice was reduced in liver, but not muscle, suggesting an organ-specific defect. Phosphorylation of components of the hepatic insulin-signaling pathway, namely IRS1, Akt, and GSK3, was decreased in LGSKO mice. Moreover, insulin stimulation of their phosphorylation was significantly suppressed, both temporally and in an insulin dose response. Phosphorylation of the insulin-regulated transcription factor FoxO1 was somewhat reduced and insulin treatment did not elicit normal translocation of FoxO1 out of the nucleus. Fat overaccumulated in LGSKO livers, showing an aberrant distribution in the acinus, an increase not explained by a reduction in hepatic triglyceride export. Rather, when administered orally to fasted mice, glucose was directed toward hepatic lipogenesis as judged by the activity, protein levels, and expression of several fatty acid synthesis genes, namely, acetyl-CoA carboxylase, fatty acid synthase, SREBP1c, chREBP, glucokinase, and pyruvate kinase. Furthermore, using cultured primary hepatocytes, we found that lipogenesis was increased by 40% in LGSKO cells compared with controls. Of note, the hepatic insulin resistance was not associated with increased levels of pro-inflammatory markers. Our results suggest that loss of liver glycogen synthesis diverts glucose toward fat synthesis, correlating with impaired hepatic insulin signaling and glucose disposal.

Redox Switch for the Inhibited State of Yeast Glycogen Synthase Mimics Regulation by Phosphorylation.

Glycogen synthase (GS) is the rate limiting enzyme in the synthesis of glycogen. Eukaryotic GS is negatively regulated by covalent phosphorylation and allosterically activated by glucose-6-phosphate (G-6-P). To gain structural insights into the inhibited state of the enzyme, we solved the crystal structure of yGsy2-R589A/R592A to a resolution of 3.3 Å. The double mutant has an activity ratio similar to the phosphorylated enzyme and also retains the ability to be activated by G-6-P. When compared to the 2.88 Å structure of the wild-type G-6-P activated enzyme, the crystal structure of the low-activity mutant showed that the N-terminal domain of the inhibited state is tightly held against the dimer-related interface thereby hindering acceptor access to the catalytic cleft. On the basis of these two structural observations, we developed a reversible redox regulatory feature in yeast GS by substituting cysteine residues for two highly conserved arginine residues. When oxidized, the cysteine mutant enzyme exhibits activity levels similar to the phosphorylated enzyme but cannot be activated by G-6-P. Upon reduction, the cysteine mutant enzyme regains normal activity levels and regulatory response to G-6-P activation.

Novel method for detection of glycogen in cells.

y: Glycogen, a branched polymer of glucose, functions as an energy reserve in many living organisms. Abnormalities in glycogen metabolism, usually excessive accumulation, can be caused genetically, most often through mutation of the enzymes directly involved in synthesis and degradation of the polymer leading to a variety of glycogen storage diseases (GSDs). Microscopic visualization of glycogen deposits in cells and tissues is important for the study of normal glycogen metabolism as well as diagnosis of GSDs. Here, we describe a method for the detection of glycogen using a renewable, recombinant protein which contains the carbohydrate-binding module (CBM) from starch-binding domain containing protein 1 (Stbd1). We generated a fusion protein containing g lutathione S-transferase, a cM c eptitope and the tbd1 BM (GYSC) for use as a glycogen-binding probe, which can be detected with secondary antibodies against glutathione S-transferase or cMyc. By enzyme-linked immunosorbent assay, we demonstrate that GYSC binds glycogen and two other polymers of glucose, amylopectin and amylose. Immunofluorescence staining of cultured cells indicate a GYSC-specific signal that is co-localized with signals obtained with anti-glycogen or anti-glycogen synthase antibodies. GYSC-positive staining inside of lysosomes is observed in individual muscle fibers isolated from mice deficient in lysosomal enzyme acid alpha-glucosidase, a well-characterized model of GSD II (Pompe disease). Co-localized GYSC and glycogen signals are also found in muscle fibers isolated from mice deficient in malin, a model for Lafora disease. These data indicate that GYSC is a novel probe that can be used to study glycogen metabolism under normal and pathological conditions.

Glycogen phosphomonoester distribution in mouse models of the progressive myoclonic epilepsy, Lafora disease.

Glycogen is a branched polymer of glucose that acts as an energy reserve in many cell types. Glycogen contains trace amounts of covalent phosphate, in the range of 1 phosphate per 500-2000 glucose residues depending on the source. The function, if any, is unknown, but in at least one genetic disease, the progressive myoclonic epilepsy Lafora disease, excessive phosphorylation of glycogen has been implicated in the pathology by disturbing glycogen structure. Some 90% of Lafora cases are attributed to mutations of the EPM2A or EPM2B genes, and mice with either gene disrupted accumulate hyperphosphorylated glycogen. It is, therefore, of importance to understand the chemistry of glycogen phosphorylation. Rabbit skeletal muscle glycogen contained covalent phosphate as monoesters of C2, C3, and C6 carbons of glucose residues based on analyses of phospho-oligosaccharides by NMR. Furthermore, using a sensitive assay for glucose 6-P in hydrolysates of glycogen coupled with measurement of total phosphate, we determined the proportion of C6 phosphorylation in rabbit muscle glycogen to be ∼20%. C6 phosphorylation also accounted for ∼20% of the covalent phosphate in wild type mouse muscle glycogen. Glycogen phosphorylation in Epm2a(-/-) and Epm2b(-/-) mice was increased 8- and 4-fold compared with wild type mice, but the proportion of C6 phosphorylation remained unchanged at ∼20%. Therefore, our results suggest that C2, C3, and/or C6 phosphate could all contribute to abnormal glycogen structure or to Lafora disease.

Muscle glycogen remodeling and glycogen phosphate metabolism following exhaustive exercise of wild type and laforin knockout mice.

Glycogen, the repository of glucose in many cell types, contains small amounts of covalent phosphate, of uncertain function and poorly understood metabolism. Loss-of-function mutations in the laforin gene cause the fatal neurodegenerative disorder, Lafora disease, characterized by increased glycogen phosphorylation and the formation of abnormal deposits of glycogen-like material called Lafora bodies. It is generally accepted that the phosphate is removed by the laforin phosphatase. To study the dynamics of skeletal muscle glycogen phosphorylation in vivo under physiological conditions, mice were subjected to glycogen-depleting exercise and then monitored while they resynthesized glycogen. Depletion of glycogen by exercise was associated with a substantial reduction in total glycogen phosphate and the newly resynthesized glycogen was less branched and less phosphorylated. Branching returned to normal on a time frame of days, whereas phosphorylation remained suppressed over a longer period of time. We observed no change in markers of autophagy. Exercise of 3-month-old laforin knock-out mice caused a similar depletion of glycogen but no loss of glycogen phosphate. Furthermore, remodeling of glycogen to restore the basal branching pattern was delayed in the knock-out animals. From these results, we infer that 1) laforin is responsible for glycogen dephosphorylation during exercise and acts during the cytosolic degradation of glycogen, 2) excess glycogen phosphorylation in the absence of laforin delays the normal remodeling of the branching structure, and 3) the accumulation of glycogen phosphate is a relatively slow process involving multiple cycles of glycogen synthesis-degradation, consistent with the slow onset of the symptoms of Lafora disease.

Incorporation of phosphate into glycogen by glycogen synthase.

The storage polymer glycogen normally contains small amounts of covalently attached phosphate as phosphomonoesters at C2, C3 and C6 atoms of glucose residues. In the absence of the laforin phosphatase, as in the rare childhood epilepsy Lafora disease, the phosphorylation level is elevated and is associated with abnormal glycogen structure that contributes to the pathology. Laforin therefore likely functions in vivo as a glycogen phosphatase. The mechanism of glycogen phosphorylation is less well-understood. We have reported that glycogen synthase incorporates phosphate into glycogen via a rare side reaction in which glucose-phosphate rather than glucose is transferred to a growing polyglucose chain (Tagliabracci et al. (2011) Cell Metab13, 274-282). We proposed a mechanism to account for phosphorylation at C2 and possibly at C3. Our results have since been challenged (Nitschke et al. (2013) Cell Metab17, 756-767). Here we extend the evidence supporting our conclusion, validating the assay used for the detection of glycogen phosphorylation, measurement of the transfer of (32)P from [ß-(32)P]UDP-glucose to glycogen by glycogen synthase. The (32)P associated with the glycogen fraction was stable to ethanol precipitation, SDS-PAGE and gel filtration on Sephadex G50. The (32)P-signal was not affected by inclusion of excess unlabeled UDP before analysis or by treatment with a UDPase, arguing against the signal being due to contaminating [ß-(32)P]UDP generated in the reaction. Furthermore, [(32)P]UDP did not bind non-covalently to glycogen. The (32)P associated with glycogen was released by laforin treatment, suggesting that it was present as a phosphomonoester. The conclusion is that glycogen synthase can mediate the introduction of phosphate into glycogen, thereby providing a possible mechanism for C2, and perhaps C3, phosphorylation.

Structural basis for 2'-phosphate incorporation into glycogen by glycogen synthase.

Glycogen is a glucose polymer that contains minor amounts of covalently attached phosphate. Hyperphosphorylation is deleterious to glycogen structure and can lead to Lafora disease. Recently, it was demonstrated that glycogen synthase catalyzes glucose-phosphate transfer in addition to its characteristic glucose transfer reaction. Glucose-1,2-cyclic-phosphate (GCP) was proposed to be formed from UDP-Glc breakdown and subsequently transferred, thus providing a source of phosphate found in glycogen. To gain further insight into the molecular basis for glucose-phosphate transfer, two structures of yeast glycogen synthase were determined; a 3.0-Å resolution structure of the complex with UMP/GCP and a 2.8-Å resolution structure of the complex with UDP/glucose. Structural superposition of the complexes revealed that the bound ligands and most active site residues are positioned similarly, consistent with the use of a common transfer mechanism for both reactions. The N-terminal domain of the UDP-glucose complex was found to be 13.3° more closed compared with a UDP complex. However, the UMP · GCP complex was 4.8° less closed than the glucose complex, which may explain the low efficiency of GCP transfer. Modeling of either α- or ß-glucose or a mixture of both anomers can account for the observed electron density of the UDP-glucose complex. NMR studies of UDP-Glc hydrolysis by yeast glycogen synthase were used to verify the stereochemistry of the product, and they also showed synchronous GCP accumulation. The similarities in the active sites of glycogen synthase and glycogen phosphorylase support the idea of a common catalytic mechanism in GT-B enzymes independent of the specific reaction catalyzed.

Protein degradation and quality control in cells from laforin and malin knockout mice.

Lafora disease is a progressive myoclonus epilepsy caused by mutations in the EPM2A or EPM2B genes that encode a glycogen phosphatase, laforin, and an E3 ubiquitin ligase, malin, respectively. Lafora disease is characterized by accumulation of insoluble, poorly branched, hyperphosphorylated glycogen in brain, muscle, heart, and liver. The laforinmalin complex has been proposed to play a role in the regulation of glycogen metabolism and protein quality control. We evaluated three arms of the protein degradation/ quality control process (the autophago-lysosomal pathway, the ubiquitin-proteasomal pathway, and the endoplasmic reticulum (ER) stress response) in mouse embryonic fibroblasts from Epm2a(-/-), Epm2b(-/-), and Epm2a(-/-) Epm2b(-/-) mice. The levels of LC3-II, a marker of autophagy, were decreased in all knock-out cells as compared with wild type even though they still showed a slight response to starvation and rapamycin. Furthermore, ribosomal protein S6 kinase and S6 phosphorylation were increased. Under basal conditions there was no effect on the levels of ubiquitinated proteins in the knock-out cells, but ubiquitinated protein degradation was decreased during starvation or stress. Lack of malin (Epm2b(-/-) and Epm2a(-/-) Epm2b(-/-) cells) but not laforin (Epm2a(-/-) cells) decreased LAMP1, a lysosomal marker. CHOP expression was similar in wild type and knock-out cells under basal conditions or with ER stress-inducing agents. In conclusion, both laforin and malin knock-out cells display mTOR-dependent autophagy defects and reduced proteasomal activity but no defects in the ER stress response. We speculate that these defects may be secondary to glycogen overaccumulation. This study also suggests a malin function independent of laforin, possibly in lysosomal biogenesis and/or lysosomal glycogen disposal.

Sterol regulatory element-binding protein-1 (SREBP-1) is required to regulate glycogen synthesis and gluconeogenic gene expression in mouse liver.

Sterol regulatory element-binding protein-1 (SREBP-1) is a key transcription factor that regulates genes in the de novo lipogenesis and glycolysis pathways. The levels of SREBP-1 are significantly elevated in obese patients and in animal models of obesity and type 2 diabetes, and a vast number of studies have implicated this transcription factor as a contributor to hepatic lipid accumulation and insulin resistance. However, its role in regulating carbohydrate metabolism is poorly understood. Here we have addressed whether SREBP-1 is needed for regulating glucose homeostasis. Using RNAi and a new generation of adenoviral vector, we have silenced hepatic SREBP-1 in normal and obese mice. In normal animals, SREBP-1 deficiency increased Pck1 and reduced glycogen deposition during fed conditions, providing evidence that SREBP-1 is necessary to regulate carbohydrate metabolism during the fed state. Knocking SREBP-1 down in db/db mice resulted in a significant reduction in triglyceride accumulation, as anticipated. However, mice remained hyperglycemic, which was associated with up-regulation of gluconeogenesis gene expression as well as decreased glycolysis and glycogen synthesis gene expression. Furthermore, glycogen synthase activity and glycogen accumulation were significantly reduced. In conclusion, silencing both isoforms of SREBP-1 leads to significant changes in carbohydrate metabolism and does not improve insulin resistance despite reducing steatosis in an animal model of obesity and type 2 diabetes.

Laforin and malin knockout mice have normal glucose disposal and insulin sensitivity.

Lafora disease is a fatal, progressive myoclonus epilepsy caused in ~90% of cases by mutations in the EPM2A or EPM2B genes. Characteristic of the disease is the formation of Lafora bodies, insoluble deposits containing abnormal glycogen-like material in many tissues, including neurons, muscle, heart and liver. Because glycogen is important for glucose homeostasis, the aberrant glycogen metabolism in Lafora disease might disturb whole-body glucose handling. Indeed, Vernia et al. [Vernia, S., Heredia, M., Criado, O., Rodriguez de Cordoba, S., Garcia-Roves, P.M., Cansell, C., Denis, R., Luquet, S., Foufelle, F., Ferre, P. et al. (2011) Laforin, a dual-specificity phosphatase involved in Lafora disease, regulates insulin response and whole-body energy balance in mice. Hum. Mol. Genet., 20, 2571-2584] reported that Epm2a-/- mice had enhanced glucose disposal and insulin sensitivity, leading them to suggest that laforin, the Epm2a gene product, is involved in insulin signaling. We analyzed 3-month- and 6-7-month-old Epm2a-/- mice and observed no differences in glucose tolerance tests (GTTs) or insulin tolerance tests (ITTs) compared with wild-type mice of matched genetic background. At 3 months, Epm2b-/- mice also showed no differences in GTTs and ITTs. In the 6-7-month-old Epm2a-/- mice, there was no evidence for increased insulin stimulation of the phosphorylation of Akt, GSK-3 or S6 in skeletal muscle, liver and heart. From metabolic analyses, these animals were normal with regard to food intake, oxygen consumption, energy expenditure and respiratory exchange ratio. By dual-energy X-ray absorptiometry scan, body composition was unaltered at 3 or 6-7 months of age. Echocardiography showed no defects of cardiac function in Epm2a-/- or Epm2b-/- mice. We conclude that laforin and malin have no effect on whole-body glucose metabolism and insulin sensitivity, and that laforin is not involved in insulin signaling.

PTG depletion removes Lafora bodies and rescues the fatal epilepsy of Lafora disease.

Lafora disease is the most common teenage-onset neurodegenerative disease, the main teenage-onset form of progressive myoclonus epilepsy (PME), and one of the severest epilepsies. Pathologically, a starch-like compound, polyglucosan, accumulates in neuronal cell bodies and overtakes neuronal small processes, mainly dendrites. Polyglucosan formation is catalyzed by glycogen synthase, which is activated through dephosphorylation by glycogen-associated protein phosphatase-1 (PP1). Here we remove PTG, one of the proteins that target PP1 to glycogen, from mice with Lafora disease. This results in near-complete disappearance of polyglucosans and in resolution of neurodegeneration and myoclonic epilepsy. This work discloses an entryway to treating this fatal epilepsy and potentially other glycogen storage diseases.