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Progranulin is a chemoattractant for microglia and stimulates their endocytic activity.

ABSTRACT: Mutations resulting in progranulin haploinsufficiency cause disease in patients with a subset of frontotemporal lobar degeneration; however, the biological functions of progranulin in the brain remain unknown. To address this subject, the present study initially assessed changes in gene expression and cytokine secretion in rat primary cortical neurons treated with progranulin. Molecular pathways enriched in the progranulin gene set included cell adhesion and cell motility pathways and pathways involved in growth and development. Secretion of cytokines and several chemokines linked to chemoattraction but not inflammation were also increased from progranulin-treated primary neurons. Therefore, whether progranulin is involved in recruitment of immune cells in the brain was investigated. Localized lentiviral expression of progranulin in C57BL/6 mice resulted in an increase of Iba1-positive microglia around the injection site. Moreover, progranulin alone was sufficient to promote migration of primary mouse microglia in vitro. Primary microglia and C4B8 cells demonstrated more endocytosis of amyloid ?1-42 when treated with progranulin. These data demonstrate that progranulin acts as a chemoattractant in the brain to recruit or activate microglia and can increase endocytosis of extracellular peptides such as amyloid ?.

SUBMITTER: Pickford F

PROVIDER: S-EPMC3070582 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Progranulin is a chemoattractant for microglia and stimulates their endocytic activity.

Pickford Fiona F Marcus Jacob J Camargo Luiz Miguel LM Xiao Qiurong Q Graham Danielle D Mo Jan-Rung JR Burkhardt Matthew M Kulkarni Vinayak V Crispino Jamie J Hering Heike H Hutton Michael M

The American journal of pathology 20101223 1

Mutations resulting in progranulin haploinsufficiency cause disease in patients with a subset of frontotemporal lobar degeneration; however, the biological functions of progranulin in the brain remain unknown. To address this subject, the present study initially assessed changes in gene expression and cytokine secretion in rat primary cortical neurons treated with progranulin. Molecular pathways enriched in the progranulin gene set included cell adhesion and cell motility pathways and pathways i ...[more]

PMID: 21224065

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Project description:ObjectiveTo identify clinicopathological differences between frontotemporal lobar degeneration (FTLD) due to mutations in progranulin (FTLD-GRN) and chromosome 9 open reading frame 72 (FTLD-C9ORF72).MethodsWe performed quantitative neuropathologic comparison of 17 FTLD-C9ORF72 and 15 FTLD-GRN with a focus on microglia. For clinical comparisons, only cases with high quality medical documentation and concurring diagnoses by at least two neurologists were included (14 FTLD-GRN and 13 FTLD-C9ORF72). Neuropathological analyses were limited to TDP-43 Type A to assure consistent assessment between the groups, acknowledging that Type A is a minority of C9ORF72 patients. Furthermore, only cases with sufficient tissue from all regions were studied (11 FTLD-GRN and 11 FTLD-C9ORF72). FTLD cases were also compared to age- and sex-matched normal controls. Immunohistochemistry was performed for pTDP-43, IBA-1, CD68, and GFAP. Morphological characterization of microglia was performed in sections of cortex blinded to clinical and genetic information.ResultsFTLD-GRN patients had frequent asymmetric clinical features, including aphasia and apraxia, as well as more asymmetric cortical atrophy. Neuropathologically, FTLD-C9ORF72 had greater hippocampal tau pathology and more TDP-43 neuronal cytoplasmic inclusions. FTLD-GRN had more neocortical microvacuolation, as well as more IBA-1-positive ameboid microglia in superficial cortical layers and in subcortical white matter. FTLD-GRN also had more microglia with nuclear condensation, possibly indicating apoptosis. Microglial morphology with CD68 immunohistochemistry in FTLD-GRN and FTLD-C9ORF72 differed from controls.InterpretationOur findings underscore differences in microglial response in FTLD-C9ORF72 and FTLD-GRN as shown by significant differences in ameboid microglia in gray and white matter. These results suggest the differential contribution of microglial dysfunction in FTLD-GRN and FTLD-C9ORF72 and suggest that clinical, neuroimaging and pathologic differences could in part be related to differences in microglia response.

Project description:BackgroundHeterozygous loss-of-function mutations in the progranulin gene (GRN) lead to frontotemporal lobar degeneration (FTLD) while the complete loss of progranulin (PGRN) function results in neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disease. Thus the growth factor-like protein PGRN may play an important role in lysosomal degradation. In line with a potential lysosomal function, PGRN is partially localized and processed in lysosomes. In the central nervous system (CNS), PGRN is like other lysosomal proteins highly expressed in microglia, further supporting an important role in protein degradation. We have previously reported that cathepsin (Cat) D is elevated in GRN-associated FTLD patients and Grn knockout mice. However, the primary mechanism that causes impaired protein degradation and elevated CatD levels upon PGRN deficiency in NCL and FTLD remains unclear.MethodsmRNA expression analysis of selected lysosomal hydrolases, lysosomal membrane proteins and autophagy-related genes was performed by NanoString nCounter panel. Protein expression, maturation and in vitro activity of Cat D, B and L in mouse embryonic fibroblasts (MEF) and brains of Grn knockout mice were investigated. To selectively characterize microglial and non-microglial brain cells, an acutely isolated microglia fraction using MACS microbeads (Miltenyi Biotec) conjugated with CD11b antibody and a microglia-depleted fraction were analyzed for protein expression and maturation of selected cathepsins.ResultsWe demonstrate that loss of PGRN results in enhanced expression, maturation and in vitro activity of Cat D, B and L in mouse embryonic fibroblasts and brain extracts of aged Grn knockout mice. Consistent with an overall enhanced expression and activity of lysosomal proteases in brain of Grn knockout mice, we observed an age-dependent transcriptional upregulation of certain lysosomal proteases. Thus, lysosomal dysfunction is not reflected by transcriptional downregulation of lysosomal proteases but rather by the upregulation of certain lysosomal proteases in an age-dependent manner. Surprisingly, cell specific analyses identified early lysosomal deficits in microglia before enhanced cathepsin levels could be detected in other brain cells, suggesting different functional consequences on lysosomal homeostasis in microglia and other brain cells upon lack of PGRN.ConclusionsThe present study uncovers early and selective lysosomal dysfunctions in Grn knockout microglia/macrophages. Dysregulated lysosomal homeostasis in microglia might trigger compensatory lysosomal changes in other brain cells.

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Progranulin is a chemoattractant for microglia and stimulates their endocytic activity.

Publications

Progranulin is a chemoattractant for microglia and stimulates their endocytic activity.

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