Progranulin Does Not Bind Tumor Necrosis Factor (TNF) Receptors and Is Not a Direct Regulator of TNF-Dependent Signaling or Bioactivity in Immune or Neuronal Cells

Abstract

Progranulin (PGRN) is a secreted glycoprotein expressed in neurons and glia that is implicated in neuronal survival on the basis that mutations in the GRN gene causing haploinsufficiency result in a familial form of frontotemporal dementia (FTD). Recently, a direct interaction between PGRN and tumor necrosis factor receptors (TNFR I/II) was reported and proposed to be a mechanism by which PGRN exerts anti-inflammatory activity, raising the possibility that aberrant PGRN–TNFR interactions underlie the molecular basis for neuroinflammation in frontotemporal lobar degeneration pathogenesis. Here, we report that we find no evidence for a direct physical or functional interaction between PGRN and TNFRs. Using coimmunoprecipitation and surface plasmon resonance (SPR) we replicated the interaction between PGRN and sortilin and that between TNF and TNFRI/II, but not the interaction between PGRN and TNFRs. Recombinant PGRN or transfection of a cDNA encoding PGRN did not antagonize TNF-dependent NFκB, Akt, and Erk1/2 pathway activation; inflammatory gene expression; or secretion of inflammatory factors in BV2 microglia and bone marrow-derived macrophages (BMDMs). Moreover, PGRN did not antagonize TNF-induced cytotoxicity on dopaminergic neuroblastoma cells. Last, co-addition or pre-incubation with various N- or C-terminal-tagged recombinant PGRNs did not alter lipopolysaccharide-induced inflammatory gene expression or cytokine secretion in any cell type examined, including BMDMs from Grn+/− or Grn−/− mice. Therefore, the neuroinflammatory phenotype associated with PGRN deficiency in the CNS is not a direct consequence of the loss of TNF antagonism by PGRN, but may be a secondary response by glia to disrupted interactions between PGRN and Sortilin and/or other binding partners yet to be identified.

Progranulin deficiency induces overactivation of WNT5A expression via TNF-α/NF-κB pathway in peripheral cells from frontotemporal dementia-linked granulin mutation carriers

“…37 Other authors did not find evidence for a direct interaction between PGRN and TNFRs; 67 however, their inability to demonstrate the direct binding of PGRN to the TNFRs could have been due to improper folding of the rhP-GRN used or to inappropriate chip selection for the surface plasmon resonance. Since then, several groups independently confirmed the PGRN-TNFR interaction and the inhibitory effect of this binding on TNF-α-induced effects.…”

Administration of progranulin (PGRN) triggers ER stress and impairs insulin sensitivity via PERK-eIF2α-dependent manner

“…Some report that PGRN action is not mediated through TNFR, 49,50 while more studies suggest that PGRN is a TNFR antagonist or a co-factor for TNFa action. 51 Recently, it has been shown that PGRN binds to TNFR, interfering with the interaction between TNFa and TNFR.…”

Antibody against Granulin–Epithelin Precursor Sensitizes Hepatocellular Carcinoma to Chemotherapeutic Agents

“…41) and the potential role of GEP antibody in patients with arthritis (42). Nonetheless, the binding of GEP and TNFR in different cell types and the functional roles remain to be elucidated (43,44). This study demonstrated that GEP antibody sensitized HCC cells to chemotherapeutic agents through disruption of Akt/Bcl-2 apoptosis signaling, inhibition of drug efflux through suppression of GEP/ABCB5.…”