492 research outputs found

    Progranulin contributes to endogenous mechanisms of pain defense after nerve injury in mice

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    Progranulin haploinsufficiency is associated with frontotemporal dementia in humans. Deficiency of progranulin led to exaggerated inflammation and premature aging in mice. The role of progranulin in adaptations to nerve injury and neuropathic pain are still unknown. Here we found that progranulin is up-regulated after injury of the sciatic nerve in the mouse ipsilateral dorsal root ganglia and spinal cord, most prominently in the microglia surrounding injured motor neurons. Progranulin knockdown by continuous intrathecal spinal delivery of small interfering RNA after sciatic nerve injury intensified neuropathic pain-like behaviour and delayed the recovery of motor functions. Compared to wild-type mice, progranulin-deficient mice developed more intense nociceptive hypersensitivity after nerve injury. The differences escalated with aging. Knockdown of progranulin reduced the survival of dissociated primary neurons and neurite outgrowth, whereas addition of recombinant progranulin rescued primary dorsal root ganglia neurons from cell death induced by nerve growth factor withdrawal. Thus, up-regulation of progranulin after neuronal injury may reduce neuropathic pain and help motor function recovery, at least in part, by promoting survival of injured neurons and supporting regrowth. A deficiency in this mechanism may increase the risk for injury-associated chronic pain

    Age- and stress-associated C. elegans granulins impair lysosomal function and induce a compensatory HLH-30/TFEB transcriptional response.

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    The progressive failure of protein homeostasis is a hallmark of aging and a common feature in neurodegenerative disease. As the enzymes executing the final stages of autophagy, lysosomal proteases are key contributors to the maintenance of protein homeostasis with age. We previously reported that expression of granulin peptides, the cleavage products of the neurodegenerative disease protein progranulin, enhance the accumulation and toxicity of TAR DNA binding protein 43 (TDP-43) in Caenorhabditis elegans (C. elegans). In this study we show that C. elegans granulins are produced in an age- and stress-dependent manner. Granulins localize to the endolysosomal compartment where they impair lysosomal protease expression and activity. Consequently, protein homeostasis is disrupted, promoting the nuclear translocation of the lysosomal transcription factor HLH-30/TFEB, and prompting cells to activate a compensatory transcriptional program. The three C. elegans granulin peptides exhibited distinct but overlapping functional effects in our assays, which may be due to amino acid composition that results in distinct electrostatic and hydrophobicity profiles. Our results support a model in which granulin production modulates a critical transition between the normal, physiological regulation of protease activity and the impairment of lysosomal function that can occur with age and disease

    Multiple-locus heterozygosity, physiology and growth at two different stages in the life cycle of the Chilean oyster Ostrea chilensis

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    A random sample of 150 individuals of a laboratory-produced cohort of Ostrea chilensis Philippi, 1845 was taken at 10 and 36 mo of age to estimate physiological variables and individual heterozygosity using 4 loci (Lap, Pgi, Pgm and Ca). Juveniles of 10 mo of age showed a mean D value of 0.134 (p > 0.05) and a positive correlation between oyster size and multiple-locus heterozygosity (MLH) (p 0.05), oxygen consumption rate (p < 0.05) and MLH was found. The K2 value (standardized net growth efficiency) was positively correlated (p < 0.05) with MLH. At 36 mo a heterozygote deficiency was present with a mean value D = -0.431 (p < 0.05). No relationship between standard dry weight and MLH and also a negative correlation between the scope for growth and MLH were found. The oxygen consumption and excretion rates also showed an increase in large size individuals. The slopes for filtration and excretion rates against MLH were negative and not statistically significant. However, ingestion and absorption rates showed significant (p < 0.05) decrease with an increase in heterozygosity. The results seem to indicate that within sexually immature individuals of O. chilensis, a positive correlation between growth rate and MLH can be found, while in adults the higher energy allocation for reproduction precludes the detection of this relationship

    Lysosomal dysfunction and microglial hyperactivation in models of progranulin deficiency

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    In my thesis I focused on the pivotal role of microglia in neurodegenerative disease, their different activation stages upon progranulin (PGRN) or triggering receptor expressed on myeloid cells 2 (TREM2) deficiency and the connection between lysosomal deficiency and microglial hyperactivation. Microglia majorly contribute to the progression and pathology of neurodegenerative disorders like Alzheimer`s disease (AD) and frontotemporal lobal degeneration (FTLD) and additionally recent advances of genome wide association studies (GWAS) have identified genetic association, as rare variants of genes that are predominantly expressed by microglia increase the risk of developing neurodegenerative disease. Among these risk genes are progranulin (GRN) and the triggering receptor expressed on myeloid cells 2 (TREM2). While the heterozygous loss of PGRN leads to FTLD, the complete loss of PGRN results in the lysosomal storage disease neuronal ceroid lipofuscinosis, indicating a major role of PGRN in lysosomal protein degradation in the brain. Our laboratory has previously shown, that progranulin knockout mice (Grn-/-) and GRN-associated FTLD patients exhibit increased levels of the lysosomal protein cathepsin (Cat) D, however the exact role of PGRN in lysosomal protein degradation remained unclear. In a collaborative effort with Julia K. Götzl, Alessio-Vittorio Colombo and Kathrin Fellerer, I therefore analyzed microglia and other brain cells regarding changes in expression, maturation and enzymatic activity of lysosomal proteins like Cat D, B and L. We found a striking age-depended increase of lysosomal proteases associated with increased enzymatic activity. Interestingly, we demonstrated that microglia show early lysosomal deficits, even before enhanced Cat transcription levels were observed. Our laboratory has previously shown, that PGRN loss of function (LOF) leads to hyperactivated microglia that exhibit increased phagocytosis, proliferation and migration. The opposite microglial phenotype is found in TREM2 LOF models, where microglia appear to be locked in a homeostatic state, unable to react to pathological insults. In addition to the lysosomal dysfunction discussed above, PGRN LOF microglia also increase TREM2 expression. To test the hypothesis that hyperactivation of microglia in PGRN LOF is TREM2-dependent and that microglia can reversibly switch between activation stages, I used genetic and pharmacological TREM2 antagonistic approaches to prevent the transition of homeostatic microglia to a disease-associated microglia (DAM) state. To further investigate the microglial contribution to disease pathology in PGRN LOF models, I generated Grn x Trem2 double knockout mice to analyze the expression of DAM genes, lysosomal dysfunction, glucose uptake, lipid metabolism and microglia morphology and activation status. Here, I found that ablating TREM2 in PGRN LOF mice reduces the expression of DAM genes, suggesting that suppression of TREM2 can lower microglia hyperactivation and is likely to be upstream PGRN-mediated microglial transcriptional changes. To further explore whether pharmacological modulation of TREM2 has beneficial functions on microglia states, I used antibodies antagonistic for TREM2, developed at Denali Therapeutics, to treat macrophages isolated from GRN-FTLD patients. Treatment of the cells with these antibodies resulted in reduced TREM2 signaling, due to its enhanced shedding. To confirm these findings, I collaborated with Sophie Robinson, who generated PGRN-deficient microglia derived from human-induced pluripotent stem cells (iPSC). Treatment of these cells with antagonistic TREM2 antibodies resulted in reduced microglia hyperactivation, TREM2 signaling and phagocytic activity. However, we did not observe any effects on lysosomal dysfunction in PGRN deficient iPSC after antibody treatment. In line with this, Grn x Trem2 double knockout mice not only failed to rescue effects on lysosomal dysfunction, lipid metabolism and microglia morphology, but also further increased synaptic loss and neurofilament light-chain (Nfl) levels, a marker of neuronal damage in the brain. My results suggest that with PGRN deficiency, lysosomal dysfunction is upstream to the microglia hyperactivation. In addition, these findings imply a protective role of TREM2-dependent chronic activation of microglia and show the dynamic nature of microglia kinetics and their ability to reversibly switch between activation stages

    Progranulin as a biomarker and potential therapeutic agent

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    Progranulin is a cysteine-rich secreted protein with diverse pleiotropic actions and participates in several processes, such as inflammation or tumorigenesis. Progranulin was first identified as a growth factor and, recently, it was characterised as an adipokine implicated in obesity, insulin resistance and rheumatic disease. At a central level, progranulin acts as a neurotropic and neuroprotective factor and protects from neural degeneration. In this review, we summarise the most recent research advances concerning the potential role of progranulin as a therapeutic target and biomarker in cancer, neurodegenerative and inflammatory diseases

    Exaggerated inflammation, impaired host defense, and neuropathology in progranulin-deficient mice

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    Progranulin (PGRN) is a widely expressed protein involved in diverse biological processes. Haploinsufficiency of PGRN in the human causes tau-negative, ubiquitin-positive frontotemporal dementia (FTD). However, the mechanisms are unknown. To explore the role of PGRN in vivo, we generated PGRN-deficient mice. Macrophages from these mice released less interleukin-10 and more inflammatory cytokines than wild type (WT) when exposed to bacterial lipopolysaccharide. PGRN-deficient mice failed to clear Listeria monocytogenes infection as quickly as WT and allowed bacteria to proliferate in the brain, with correspondingly greater inflammation than in WT. PGRN-deficient macrophages and microglia were cytotoxic to hippocampal cells in vitro, and PGRN-deficient hippocampal slices were hypersusceptible to deprivation of oxygen and glucose. With age, brains of PGRN-deficient mice displayed greater activation of microglia and astrocytes than WT, and their hippocampal and thalamic neurons accumulated cytosolic phosphorylated transactivation response element DNA binding protein–43. Thus, PGRN is a key regulator of inflammation and plays critical roles in both host defense and neuronal integrity. FTD associated with PGRN insufficiency may result from many years of reduced neutrotrophic support together with cumulative damage in association with dysregulated inflammation

    Progranulin, a Glycoprotein Deficient in Frontotemporal Dementia, Is a Novel Substrate of Several Protein Disulfide Isomerase Family Proteins

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    The reduced production or activity of the cysteine-rich glycoprotein progranulin is responsible for about 20% of cases of familial frontotemporal dementia. However, little is known about the molecular mechanisms that govern the level and secretion of progranulin. Here we show that progranulin is expressed in mouse cortical neurons and more prominently in mouse microglia in culture and is abundant in the endoplasmic reticulum (ER) and Golgi. Using chemical crosslinking, immunoprecipitation, and mass spectrometry, we found that progranulin is bound to a network of ER Ca2+-binding chaperones including BiP, calreticulin, GRP94, and four members of the protein disulfide isomerase (PDI) family. Loss of ERp57 inhibits progranulin secretion. Thus, progranulin is a novel substrate of several PDI family proteins and modulation of the ER chaperone network may be a therapeutic target for controlling progranulin secretion
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