Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 14 de 14
Filter
Add more filters










Publication year range
1.
FASEB J ; 34(5): 6675-6687, 2020 05.
Article in English | MEDLINE | ID: mdl-32237095

ABSTRACT

The triggering receptor expressed on myeloid cells 2 (TREM2) is a multifunctional surface protein that affects survival, migration, and phagocytic capacity of myeloid cells. Soluble TREM2 levels were found to be increased in early stages of sporadic and familial Alzheimer's disease (AD) probably reflecting a defensive microglial response to some initial brain damage. The disintegrin and metalloproteases (ADAM) 10 and 17 were identified as TREM2 sheddases. We demonstrate that meprin ß is a direct TREM2 cleaving enzyme using ADAM10/17 deficient HEK293 cells. LC-MS/MS analysis of recombinant TREM2 incubated with meprin ß revealed predominant cleavage between Arg136 and Asp137, distant to the site identified for ADAM10/17. We further demonstrate that the metalloprotease meprin ß cleaves TREM2 on macrophages concomitant with decreased levels of soluble TREM2 in the serum of Mep1b-/- mice compared to WT controls. Isolated BMDMs from Mep1b-/- mice showed significantly increased full-length TREM2 levels and enhanced phagocytosis efficiency compared to WT cells. The diminished constitutive shedding of TREM2 on meprin ß deficient macrophages could be rescued by ADAM stimulation through LPS treatment. Our data provide evidence that meprin ß is a TREM2 sheddase on macrophages and suggest that multiple proteases may be involved in the generation of soluble TREM2.


Subject(s)
Macrophages/physiology , Membrane Glycoproteins/metabolism , Metalloendopeptidases/physiology , Phagocytosis , Receptors, Immunologic/metabolism , Animals , Arginine/metabolism , Aspartic Acid/metabolism , Macrophages/cytology , Male , Membrane Glycoproteins/genetics , Mice , Mice, Knockout , Receptors, Immunologic/genetics
2.
Heliyon ; 4(10): e00826, 2018 Oct.
Article in English | MEDLINE | ID: mdl-30302409

ABSTRACT

Over the last years, studies on microglia cell function in chronic neuro-inflammation and neuronal necrosis pointed towards an eminent role of these cells in Multiple Sclerosis, Parkinson's and Alzheimer's Disease. It was found, that microglia cell activity can be stimulated towards a pro- or an anti-inflammatory profile, depending on the stimulating signals. Therefore, investigation of receptors expressed by microglia cells and ligands influencing their activation state is of eminent interest. A receptor found to be expressed by microglia cells is the mineralocorticoid receptor. One of its ligands is Aldosterone, a naturally produced steroid hormone of the adrenal cortex, which mainly induces homeostatic and renal effects. We evaluated if the addition of Aldosterone to LPS stimulated microglia cells changes their inflammatory profile. Therefore, we assessed the levels of nitric oxide (NO), iNOS, IL-6, IL-1ß, TNF-α and COX-2 in untreated, LPS-treated and LPS/Aldosterone-treated microglia cells. Furthermore we analyzed p38-MAP-Kinase and NFκB signaling within these cells. Our results indicate that the co-stimulation with Aldosterone leads to a decrease of the LPS-induced pro-inflammatory effect and thus renders Aldosterone an anti-inflammatory agent in our model system.

3.
Oncotarget ; 8(27): 43635-43652, 2017 Jul 04.
Article in English | MEDLINE | ID: mdl-28504966

ABSTRACT

The Transmembrane protein 192 (TMEM192) is a lysosomal/late endosomal protein initially discovered by organellar proteomics. TMEM192 exhibits four transmembrane segments with cytosolic N- and C-termini and forms homodimers. Devoid of significant homologies, the molecular function of TMEM192 is currently unknown. Upon TMEM192 knockdown in hepatoma cells, a dysregulation of autophagy and increased apoptosis were reported. Here, we aimed to define the physiological role of TMEM192 by analysing consequences of TMEM192 ablation in mice. Therefore, we compared the biochemical properties of murine TMEM192 to those of the human orthologue. We reveal lysosomal residence of murine TMEM192 and demonstrate ubiquitous tissue expression. In brain, TMEM192 expression was pronounced in the hippocampus but also present in the cortex and cerebellum, as analysed based on a lacZ reporter allele. Murine TMEM192 undergoes proteolytic processing in a tissue-specific manner. Thereby, a 17 kDa fragment is generated which was detected in most murine tissues except liver. TMEM192 processing occurs after lysosomal targeting by pH-dependent lysosomal proteases. TMEM192-/- murine embryonic fibroblasts (MEFs) exhibited a regular morphology of endo-/lysosomes and were capable of performing autophagy and lysosomal exocytosis. Histopathological, ultrastructural and biochemical analyses of all major tissues of TMEM192-/- mice demonstrated normal lysosomal functions without apparent lysosomal storage. Furthermore, the abundance of the major immune cells was comparable in TMEM192-/- and wild type mice. Based on this, we conclude that under basal conditions in vivo the loss of TMEM192 can be efficiently compensated by alternative pathways. Further studies will be required to decipher its molecular function.


Subject(s)
Intracellular Membranes/metabolism , Lysosomes/metabolism , Membrane Proteins/metabolism , Animals , Autophagy , Brain/metabolism , Brain/pathology , Cell Line, Tumor , Fibroblasts , Gene Expression , Gene Knockout Techniques , Glycosylation , Liver/metabolism , Liver/pathology , Membrane Proteins/genetics , Mice , Mice, Knockout , Proteolysis , Spleen/metabolism , Spleen/pathology , Ubiquitination
4.
J Immunol ; 199(1): 172-185, 2017 07 01.
Article in English | MEDLINE | ID: mdl-28550201

ABSTRACT

The invariant chain (CD74) mediates assembly and targeting of MHC class II (MHCII) complexes. In endosomes, CD74 undergoes sequential degradation by different proteases, including cathepsin S (CatS) and the intramembrane protease signal peptide peptidase-like 2a (SPPL2a). In their absence, CD74 N-terminal fragments (NTFs) accumulate. In SPPL2a-/- B cells, such an NTF impairs endosomal trafficking and BCR signal transduction. In mice, this leads to a loss of splenic B cells beyond the transitional stage 1. To gain insight into CD74 determinants and the role of MHCII, we compared B cells from CatS-/- , SPPL2a-/- , and SPPL2a-MHCII double-deficient mice. We assessed differentiation of B cells in bone marrow and spleen and analyzed their endosomal morphology, BCR expression, and signal transduction. We demonstrate that MHCII is dispensable for the B cell phenotype of SPPL2a-/- mice, further supporting a CD74-intrinsic effect. Despite significant vacuolization of endosomal compartments similar to SPPL2a-/- B cells, CatS-/- traditional stage 1 B cells show unimpaired degradation of endocytic cargo, have intact BCR signaling, and do not exhibit any relevant defects in maturation. This could indicate that CD74 NTF-induced structural changes of endosomes are not directly involved in these processes. We further found that the block of CD74 degradation in CatS-/- B cells is incomplete, so that NTF levels are significantly lower than in SPPL2a-/- B cells. This suggests a dose dependency and threshold for the CD74 NTF-associated impairment of B cell signaling and maturation. In addition, different functional properties of the longer, MHCII-bound CD74 NTF could contribute to the milder phenotype of CatS-/- B cells.


Subject(s)
Antigens, Differentiation, B-Lymphocyte/immunology , B-Lymphocytes/immunology , Genes, MHC Class II , Histocompatibility Antigens Class II/immunology , Animals , Antigens, Differentiation, B-Lymphocyte/metabolism , Aspartic Acid Endopeptidases/deficiency , Aspartic Acid Endopeptidases/genetics , Aspartic Acid Endopeptidases/metabolism , Cathepsins/deficiency , Cathepsins/genetics , Cathepsins/metabolism , Cell Differentiation , Endosomes/immunology , Endosomes/physiology , Histocompatibility Antigens Class II/metabolism , Membrane Proteins/deficiency , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice , Signal Transduction
5.
Cell Calcium ; 65: 8-13, 2017 07.
Article in English | MEDLINE | ID: mdl-28365001

ABSTRACT

The two metalloproteases meprin ß and bone morphogenetic protein 1 (BMP-1) are both members of the astacin protease family. They share specificity for negatively charged residues around the scissile bond and they are expressed in overlapping compartments of the human body. One important proteolytic substrate they share is pro-collagen I. Ablation of one of the two proteases however leads to different collagen I associated phenotypes in vivo. Over the last years calcium emerged as a regulator for the proteolytic activity of both enzymes. For meprin ß a reduction and for BMP-1 an increase in activity was reported under increasing calcium concentrations. Here we revisit different compartments that rely on pro-collagen I maturation and explore the crystal structure of both proteases to highlight possible calcium binding sites. With this we aim to emphasize a to date underestimated regulator that influences both proteases.


Subject(s)
Bone Morphogenetic Protein 1/chemistry , Calcium Chloride/chemistry , Metalloendopeptidases/chemistry , Bone Morphogenetic Protein 1/metabolism , Collagen Type I/chemistry , Collagen Type I/metabolism , Humans , Metalloendopeptidases/metabolism
6.
Sci Rep ; 7: 44053, 2017 03 09.
Article in English | MEDLINE | ID: mdl-28276471

ABSTRACT

Soluble Interleukin-6 receptor (sIL-6R) mediated trans-signaling is an important pro-inflammatory stimulus associated with pathological conditions, such as arthritis, neurodegeneration and inflammatory bowel disease. The sIL-6R is generated proteolytically from its membrane bound form and A Disintegrin And Metalloprotease (ADAM) 10 and 17 were shown to perform ectodomain shedding of the receptor in vitro and in vivo. However, under certain conditions not all sIL-6R could be assigned to ADAM10/17 activity. Here, we demonstrate that the IL-6R is a shedding substrate of soluble meprin α and membrane bound meprin ß, resulting in bioactive sIL-6R that is capable of inducing IL-6 trans-signaling. We determined cleavage within the N-terminal part of the IL-6R stalk region, distinct from the cleavage site reported for ADAM10/17. Interestingly, meprin ß can be shed from the cell surface by ADAM10/17 and the observation that soluble meprin ß is not capable of shedding the IL-6R suggests a regulatory mechanism towards trans-signaling. Additionally, we observed a significant negative correlation of meprin ß expression and IL-6R levels on human granulocytes, providing evidence for in vivo function of this proteolytic interaction.


Subject(s)
Metalloendopeptidases/metabolism , Receptors, Interleukin-6/metabolism , Signal Transduction , ADAM10 Protein/genetics , ADAM10 Protein/metabolism , ADAM17 Protein/genetics , ADAM17 Protein/metabolism , Amyloid Precursor Protein Secretases/genetics , Amyloid Precursor Protein Secretases/metabolism , HEK293 Cells , Humans , Membrane Proteins/genetics , Membrane Proteins/metabolism , Metalloendopeptidases/genetics , Receptors, Interleukin-6/genetics , Solubility
7.
Cell Tissue Res ; 365(1): 3-11, 2016 07.
Article in English | MEDLINE | ID: mdl-26899249

ABSTRACT

Microglial cells are a major source of pro-inflammatory cytokines during central nervous system (CNS) inflammation. They can develop a pro-inflammatory M1 phenotype and an anti-inflammatory M2 phenotype. Shifting the phenotype from M1 to M2 might be an important mechanism to overcome CNS inflammation and to prevent or reduce neuronal damage. Here, we demonstrate that the anti-inflammatory protein trefoil factor 3 (TFF3) is secreted by astrocytes and that its transcription is significantly reduced after incubation with lipopolysaccharide (LPS). Moreover, we demonstrate that microglial cells cultured in the presence of TFF3 show reduced expression and secretion of pro-inflammatory cytokines after LPS stimulation.


Subject(s)
Anti-Inflammatory Agents/pharmacology , Microglia/pathology , Trefoil Factor-3/pharmacology , Animals , Astrocytes/drug effects , Astrocytes/pathology , Electrophoresis, Agar Gel , Microglia/drug effects , Rats, Wistar , Reverse Transcriptase Polymerase Chain Reaction
8.
J Immunol ; 195(4): 1548-63, 2015 Aug 15.
Article in English | MEDLINE | ID: mdl-26157172

ABSTRACT

The invariant chain (CD74), a chaperone in MHC class II-mediated Ag presentation, is sequentially processed by different endosomal proteases. We reported recently that clearance of the final membrane-bound N-terminal fragment (NTF) of CD74 is mediated by the intramembrane protease signal peptide peptidase-like (SPPL)2a, a process critical for B cell development. In mice, SPPL2a deficiency provokes the accumulation of this NTF in endocytic vesicles, which leads to a B cell maturation arrest at the transitional 1 stage. To define the underlying mechanism, we analyzed the impact of SPPL2a deficiency on signaling pathways involved in B cell homeostasis. We demonstrate that tonic as well as BCR-induced activation of the PI3K/Akt pathway is massively compromised in SPPL2a(-/-) B cells and identify this as major cause of the B cell maturation defect in these mice. Altered BCR trafficking induces a reduction of surface IgM in SPPL2a-deficient B cells, leading to a diminished signal transmission via the BCR and the tyrosine kinase Syk. We provide evidence that in SPPL2a(-/-) mice impaired BCR signaling is to a great extent provoked by the accumulating CD74 NTF, which can interact with the BCR and Syk, and that impaired PI3K/Akt signaling and reduced surface IgM are not directly linked processes. In line with disturbances in PI3K/Akt signaling, SPPL2a(-/-) B cells show a dysregulation of the transcription factor FOXO1, causing elevated transcription of proapoptotic genes. We conclude that SPPL2a-mediated processing of CD74 NTF is indispensable to maintain appropriate levels of tonic BCR signaling to promote B cell maturation.


Subject(s)
Antigens, Differentiation, B-Lymphocyte/metabolism , Aspartic Acid Endopeptidases/metabolism , B-Lymphocytes/metabolism , Histocompatibility Antigens Class II/metabolism , Membrane Proteins/metabolism , Receptors, Antigen, B-Cell/metabolism , Signal Transduction , Animals , Antigens, Differentiation, B-Lymphocyte/chemistry , Apoptosis/genetics , Aspartic Acid Endopeptidases/deficiency , Aspartic Acid Endopeptidases/genetics , B-Lymphocytes/cytology , B-Lymphocytes/immunology , Cell Differentiation , Cell Membrane/metabolism , Endocytosis/genetics , Endocytosis/immunology , Forkhead Box Protein O1 , Forkhead Transcription Factors/metabolism , Histocompatibility Antigens Class II/chemistry , Immunoglobulin M/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Lymphocyte Activation , MAP Kinase Signaling System , Membrane Proteins/deficiency , Membrane Proteins/genetics , Mice , Mice, Knockout , NF-kappa B/metabolism , NF-kappa B p52 Subunit/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Phosphorylation , Precursor Cells, B-Lymphoid/cytology , Precursor Cells, B-Lymphoid/metabolism , Protein Binding , Protein Interaction Domains and Motifs , Protein-Tyrosine Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Syk Kinase
9.
Biochem Biophys Res Commun ; 451(1): 48-53, 2014 Aug 15.
Article in English | MEDLINE | ID: mdl-25035924

ABSTRACT

The invariant chain (CD74) mediates targeting of the MHCII complex to endosomal compartments, where CD74 undergoes degradation allowing MHCII to acquire peptides. We demonstrated recently that intramembrane proteolysis of the final membrane-bound N-terminal fragment (NTF) of CD74 is catalyzed by Signal-peptide-peptidase-like 2a (SPPL2a) and that this process is indispensable for development and function of B lymphocytes in mice. In SPPL2a(-/-) mice, homeostasis of these cells is disturbed by the accumulation of the unprocessed CD74 NTF. So far, evidence for this essential role of SPPL2a is restricted to mice. Nevertheless, inhibition of SPPL2a has been suggested as novel approach to target B cells for treating autoimmunity. Here, we characterize human B cell lines with a homozygous microdeletion on chromosome 15. We demonstrate that this deletion disrupts the SPPL2a genomic locus and leads to loss of SPPL2a transcript. Lymphoblastoid cell lines from patients with this deletion exhibit absence of SPPL2a at the protein level and show an accumulation of the CD74 NTF comparable to B cells from SPPL2a(-/-) mice. By this means, we present evidence that the role of SPPL2a in CD74 proteolysis is conserved in human B cells and provide support for modulation of SPPL2a activity as a therapeutic concept.


Subject(s)
Antigens, Differentiation, B-Lymphocyte/metabolism , Aspartic Acid Endopeptidases/metabolism , B-Lymphocytes/metabolism , Chromosomes, Human, Pair 15 , Histocompatibility Antigens Class II/metabolism , Antigens, Differentiation, B-Lymphocyte/genetics , Aspartic Acid Endopeptidases/genetics , B-Lymphocytes/pathology , Cell Line , Chromosome Deletion , Histocompatibility Antigens Class II/genetics , Homozygote , Humans , Immunologic Deficiency Syndromes/genetics , Intracellular Membranes/metabolism , Peptide Fragments/genetics , Peptide Fragments/metabolism
10.
Mol Cell Biol ; 34(8): 1398-411, 2014 Apr.
Article in English | MEDLINE | ID: mdl-24492962

ABSTRACT

We reported recently that the presenilin homologue signal peptide peptidase-like 2a (SPPL2a) is essential for B cell development by cleaving the N-terminal fragment (NTF) of the invariant chain (li, CD74). Based on this, we suggested that pharmacological modulation of SPPL2a may represent a novel approach to deplete B cells in autoimmune disorders. With regard to reported overlapping substrate spectra of SPPL2a and its close homologue, SPPL2b, we investigated the role of SPPL2b in CD74 NTF proteolysis and its impact on B and dendritic cell homeostasis. In heterologous expression experiments, SPPL2b was found to cleave CD74 NTF with an efficiency similar to that of SPPL2a. For in vivo analysis, SPPL2b single-deficient and SPPL2a/SPPL2b double-deficient mice were generated and examined for CD74 NTF turnover/accumulation, B cell maturation and functionality, and dendritic cell homeostasis. We demonstrate that in vivo SPPL2b does not exhibit a physiologically relevant contribution to CD74 proteolysis in B and dendritic cells. Furthermore, we reveal that both proteases exhibit divergent subcellular localizations in B cells and different expression profiles in murine tissues. These findings suggest distinct functions of SPPL2a and SPPL2b and, based on a high abundance of SPPL2b in brain, a physiological role of this protease in the central nervous system.


Subject(s)
Aspartic Acid Endopeptidases/metabolism , Membrane Proteins/metabolism , Animals , Antigens, Differentiation, B-Lymphocyte/metabolism , Aspartic Acid Endopeptidases/genetics , B-Lymphocytes/metabolism , Brain/metabolism , Dendritic Cells/metabolism , Histocompatibility Antigens Class II/metabolism , Membrane Proteins/genetics , Mice , Mice, Knockout , Proteolysis
11.
Biochem Biophys Res Commun ; 442(3-4): 234-41, 2013 Dec 13.
Article in English | MEDLINE | ID: mdl-24239882

ABSTRACT

Adult hematopoiesis requires tightly regulated cell-cell interactions between hematopoietic cells and the bone marrow stromal microenvironment. We addressed the question if the ectodomain sheddase ADAM10 is essential to regulate adult hematopoiesis. Induced ADAM10 deletion in hematopoietic cells resulted in morphological and histological abnormalities that resemble an unclassified myeloproliferative disorder (MPD). The MPD was characterized by an expansion of granulocytic subpopulations and their infiltration of peripheral hematopoietic tissues, the development of hepatosplenomegaly with extramedullary erythropoiesis, lymphnodepathy and death of the mice around 20weeks after induction. ADAM10 expression analysis during the different stages of the MPD revealed that non-targeted hematopoietic cells repopulated the immune system of the ADAM10-deficient mice. Examination of mice with a myeloid- or epidermis-specific deletion of ADAM10 and bone marrow transplantation (BMT) experiments indicated that the development of the MPD can be triggered by non-cell autonomous effects. We found that plasma levels of clinical markers for MPD such as G-CSF, TIMP-1 and IL-16 were significantly elevated in ADAM10-deficient mice. Our findings indicate that a tightly controlled ADAM10 expression is needed to balance hematopoietic cell-fate decisions in adult mice.


Subject(s)
ADAM Proteins/physiology , Amyloid Precursor Protein Secretases/physiology , Disintegrins/physiology , Hematopoiesis/physiology , Membrane Proteins/physiology , ADAM Proteins/genetics , ADAM10 Protein , Amyloid Precursor Protein Secretases/genetics , Animals , Bone Marrow/enzymology , Bone Marrow/pathology , Disintegrins/genetics , Eczema/genetics , Eczema/pathology , Female , Hematopoiesis/genetics , Hepatomegaly/genetics , Hepatomegaly/pathology , Male , Membrane Proteins/genetics , Mice , Mice, Knockout , Myeloid Cells/enzymology , Myeloid Cells/pathology , Myeloproliferative Disorders/genetics , Myeloproliferative Disorders/pathology , Splenomegaly/genetics , Splenomegaly/pathology , Stromal Cells/enzymology , Stromal Cells/pathology , Thrombocytosis/genetics , Thrombocytosis/pathology
12.
J Bone Miner Res ; 28(7): 1622-30, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23426979

ABSTRACT

Intramembrane proteases are critically involved in signal transduction and membrane protein turnover. Signal-peptide-peptidase-like 2a (SPPL2A), a presenilin-homologue residing in lysosomes/late endosomes, cleaves type II-oriented transmembrane proteins. We recently identified SPPL2A as the enzyme controlling turnover and functions of the invariant chain (CD74) of the major histocompatibility complex II (MHCII) and demonstrated critical importance of this process for B cell development. Surprisingly, we found that SPPL2A is critical for formation of dental enamel. In Sppl2a knockout mice, enamel of the erupted incisors was chalky white and rapidly eroded after eruption. SPPL2A was found to be expressed in enamel epithelium during secretory and maturation stage amelogenesis. Mineral content of enamel in Sppl2a⁻/⁻ incisors was inhomogeneous and reduced by ∼20% compared to wild-type mice with the most pronounced reduction at the mesial side. Frequently, disruption of the enamel layer and localized detachment of the most superficial enamel layer was observed in the knockout incisors leading to an uneven enamel surface. In Sppl2a null mice, morphology and function of secretory stage ameloblasts were not noticeably different from that of wild-type mice. However, maturation stage ameloblasts showed reduced height and a characteristic undulation of the ameloblast layer with localized adherence of the cells to the outer enamel. This was reflected in a delayed and incomplete resorption of the proteinaceous enamel matrix. Thus, we conclude that intramembrane proteolysis by SPPL2A is essential for maintaining cellular homeostasis of ameloblasts. Because modulation of SPPL2A activity appears to be an attractive therapeutic target to deplete B cells and treat autoimmunity, interference with tooth enamel formation should be investigated as a possible adverse effect of pharmacological SPPL2A inhibitors in humans.


Subject(s)
Ameloblasts/enzymology , Antigens, Differentiation, B-Lymphocyte/metabolism , Aspartic Acid Endopeptidases/metabolism , Dental Enamel/enzymology , Histocompatibility Antigens Class II/metabolism , Incisor/enzymology , Membrane Proteins/metabolism , Proteolysis , Animals , Antigens, Differentiation, B-Lymphocyte/genetics , Aspartic Acid Endopeptidases/genetics , Dental Enamel/growth & development , Histocompatibility Antigens Class II/genetics , Incisor/growth & development , Membrane Proteins/genetics , Mice , Mice, Knockout
13.
J Exp Med ; 210(1): 41-58, 2013 Jan 14.
Article in English | MEDLINE | ID: mdl-23267015

ABSTRACT

Regulated intramembrane proteolysis is a central cellular process involved in signal transduction and membrane protein turnover. The presenilin homologue signal-peptide-peptidase-like 2a (SPPL2a) has been implicated in the cleavage of type 2 transmembrane proteins. We show that the invariant chain (li, CD74) of the major histocompatability class II complex (MHCII) undergoes intramembrane proteolysis mediated by SPPL2a. B lymphocytes of SPPL2a(-/-) mice accumulate an N-terminal fragment (NTF) of CD74, which severely impairs membrane traffic within the endocytic system and leads to an altered response to B cell receptor stimulation, reduced BAFF-R surface expression, and accumulation of MHCII in transitional developmental stage T1 B cells. This results in significant loss of B cell subsets beyond the T1 stage and disrupted humoral immune responses, which can be recovered by additional ablation of CD74. Hence, we provide evidence that regulation of CD74-NTF levels by SPPL2a is indispensable for B cell development and function by maintaining trafficking and integrity of MHCII-containing endosomes, highlighting SPPL2a as a promising pharmacological target for depleting and/or modulating B cells.


Subject(s)
Antigens, Differentiation, B-Lymphocyte/metabolism , Aspartic Acid Endopeptidases/metabolism , B-Lymphocytes/physiology , Endosomes/metabolism , Histocompatibility Antigens Class II/metabolism , Membrane Proteins/metabolism , Animals , Antigens, Differentiation, B-Lymphocyte/genetics , Aspartic Acid Endopeptidases/genetics , B-Cell Activation Factor Receptor/genetics , B-Cell Activation Factor Receptor/metabolism , B-Lymphocyte Subsets/metabolism , B-Lymphocytes/immunology , B-Lymphocytes/pathology , B-Lymphocytes/ultrastructure , Base Sequence , Cell Survival/genetics , Cells, Cultured , Histocompatibility Antigens Class II/genetics , Humans , Immunity, Humoral/genetics , Membrane Proteins/genetics , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Molecular Sequence Data , Peptide Fragments/metabolism , Protein Transport , Vacuoles/metabolism
14.
FEBS Lett ; 585(19): 2951-7, 2011 Oct 03.
Article in English | MEDLINE | ID: mdl-21896273

ABSTRACT

Signal-peptide-peptidase-like 2A (SPPL2a), an aspartyl intramembrane protease, has been implicated in the proteolysis of TNF-alpha, Fas Ligand and Bri2. Here, we show that endogenous SPPL2a - in agreement with overexpression studies - is localised in membranes of lysosomes/late endosomes. Furthermore, we have analysed the molecular determinants for lysosomal sorting of SPPL2a by creating chimaeric constructs between SPPL2a and its plasma membrane localised homologue SPPL2b. Lysosomal transport of SPPL2a critically depends on its cytosolic carboxyterminal tail. A canonical tyrosine-based sorting motif of the YXXø type at position 498 is sufficient to direct SPPL2a to lysosomal/late endosomal compartments. This motif accounts for the differential localisation of the homologous proteases SPPL2a and SPPL2b and thereby influences the access to substrates and biological function of SPPL2a.


Subject(s)
Amino Acid Motifs , Aspartic Acid Endopeptidases/chemistry , Aspartic Acid Endopeptidases/metabolism , Endosomes/metabolism , Lysosomes/metabolism , Membrane Proteins/metabolism , Tyrosine/metabolism , Animals , Aspartic Acid Endopeptidases/genetics , Fibroblasts/cytology , Fibroblasts/physiology , HeLa Cells , Humans , Membrane Proteins/genetics , Mice , Molecular Sequence Data , Sequence Alignment
SELECTION OF CITATIONS
SEARCH DETAIL
...