Roles and regulation of neutral sphingomyelinase-2 in cellular and pathological processes

Shamseddine, A.; Airola, Michael V.; Hannun, Yusuf A.

doi:10.1016/j.jbior.2014.10.002

Cited by 186 publications

(175 citation statements)

References 153 publications

(178 reference statements)

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“…Sphingomyelinases are enzymes characterized by their pH dependency: acid, neutral, or alkaline. Sphingomyelinases catalyze the breakdown of sphingomyelin into phosphocholine and ceramide, often in response to environmental stress or inflammatory cytokine stimuli [2,3]. Nsm2 is a membrane-associated enzyme located in the inner leaflet of the plasma membrane and Golgi membranes; this enzyme releases ceramide in the cytoplasmic leaflet of cellular membranes.…”

Section: Introductionmentioning

confidence: 99%

Mycobacterial Infection is Promoted by Neutral Sphingomyelinase 2 Regulating a Signaling Cascade Leading to Activation of β1-Integrin

Riehle

et al. 2018

Cell Physiol Biochem

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Background/Aims: Mycobacteria-induced diseases, especially tuberculosis, cause more than 1 million deaths each year, which is higher than any other single bacterial pathogen. Neutral sphingomyelinase 2 (Nsm2) has been implied in many physiological processes and diseases, but the role of Nsm2 in pathogen-host interactions and mycobacterial infections has barely been studied. Methods: We investigated the role of the Nsm2/ceramide system in systemic infection of mice and murine macrophages with Mycobacterium bovis Bacillus Calmette-Guérin (BCG) as a model for mycobacterial infection. For in vitro assays we isolated bone marrow-derived macrophages from Wildtype mice or Nsm2-heterozygous and investigated the role of Nsm2 for macrophage migration/clustering as well as the involvement of p38 mitogen-activated protein kinases (p38K), c-Jun N-terminal kinase (JNK), β1-integrin and Rac1 activity by Western blot and microscopic studies. For in vivo assays we injected mice intravenously with BCG and analyzed infected tissues for the role of Nsm2-mediated activation of β1-integrin in granuloma formation and bacterial burden. Results: Our results reveal that BCG infection of macrophages results in rapid stimulation of Nsm2. Genetic and pharmacological studies demonstrate that Nsm2 stimulates a signaling cascade via p38K and JNK to an activation of surface β1-integrin and Rac1 that leads to the formation of granuloma-like macrophages clusters in vitro and granuloma in vivo. Heterozygosity of Nsm2 in macrophages or antibody-mediated neutralization of active b1-integrin reduced macrophage clusters in vitro and granuloma formation in vivo. Most importantly, Nsm2 heterozygosity or treatment with neutralizing antibodies against β1-integrin protected mice from systemic BCG infections and chronic infections of the liver and spleen. Conclusion: The findings indicate that the Nsm2/ ceramide system plays an important role in systemic infection of mice with mycobacteria by regulating a signaling cascade via p38K, JNK, b1-integrin and Rac1.

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Section: Introductionmentioning

confidence: 99%

Mycobacterial Infection is Promoted by Neutral Sphingomyelinase 2 Regulating a Signaling Cascade Leading to Activation of β1-Integrin

Riehle

et al. 2018

Cell Physiol Biochem

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“…Rapid generation of ceramide in response to extracellular stimuli is mediated by the activation of sphingomyelinases (SMases), which hydrolyze sphingomyelin (SM), a major component of cell membranes, into ceramide and phosphocholine (3,4). Three families of SMases (acid, neutral, and alkaline) have been identified that are classified by their pH optima, subcellular localization, protein fold, and function (5)(6)(7)(8).…”

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confidence: 99%

“…Three families of SMases (acid, neutral, and alkaline) have been identified that are classified by their pH optima, subcellular localization, protein fold, and function (5)(6)(7)(8). Neutral sphingomyelinase 2 (nSMase2, product of the SMPD3 gene) is the major neutral sphingomyelinase (N-SMase) in mammalian cells for the stressinduced generation of ceramide (4). TNF-α (9-15), cell confluence (16,17), oxidative stress (18)(19)(20), and inflammation (20,21) are all potent activators of nSMase2.…”

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confidence: 99%

Structure of human nSMase2 reveals an interdomain allosteric activation mechanism for ceramide generation

Airola

Shanbhogue

Shamseddine

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Neutral sphingomyelinase 2 (nSMase2, product of the SMPD3 gene) is a key enzyme for ceramide generation that is involved in regulating cellular stress responses and exosome-mediated intercellular communication. nSMase2 is activated by diverse stimuli, including the anionic phospholipid phosphatidylserine. Phosphatidylserine binds to an integral-membrane N-terminal domain (NTD); however, how the NTD activates the C-terminal catalytic domain is unclear. Here, we identify the complete catalytic domain of nSMase2, which was misannotated because of a large insertion. We find the soluble catalytic domain interacts directly with the membrane-associated NTD, which serves as both a membrane anchor and an allosteric activator. The juxtamembrane region, which links the NTD and the catalytic domain, is necessary and sufficient for activation. Furthermore, we provide a mechanistic basis for this phenomenon using the crystal structure of the human nSMase2 catalytic domain determined at 1.85-Å resolution. The structure reveals a DNase-I-type fold with a hydrophobic track leading to the active site that is blocked by an evolutionarily conserved motif which we term the "DK switch." Structural analysis of nSMase2 and the extended N-SMase family shows that the DK switch can adopt different conformations to reposition a universally conserved Asp (D) residue involved in catalysis. Mutation of this Asp residue in nSMase2 disrupts catalysis, allosteric activation, stimulation by phosphatidylserine, and pharmacological inhibition by the lipid-competitive inhibitor GW4869. Taken together, these results demonstrate that the DK switch regulates ceramide generation by nSMase2 and is governed by an allosteric interdomain interaction at the membrane interface.sphingomyelinase | ceramide | enzyme | lipid | crystallography

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“…phingomyelin phosphodiesterase 3 (SMPD3) is a lipid-metabolizing enzyme present in the membranes of the endoplasmic reticulum and the inner leaflet of the cell membrane (1). Recently, this enzyme has been identified to be a key regulator of skeletal development (2)(3)(4)(5)(6).…”

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confidence: 99%

Smpd3 Expression in both Chondrocytes and Osteoblasts Is Required for Normal Endochondral Bone Development

Manickam

Ray

et al. 2016

Molecular and Cellular Biology

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f Sphingomyelin phosphodiesterase 3 (SMPD3), a lipid-metabolizing enzyme present in bone and cartilage, has been identified to be a key regulator of skeletal development. A homozygous loss-of-function mutation called fragilitas ossium (fro) in the Smpd3 gene causes poor bone and cartilage mineralization resulting in severe congenital skeletal deformities. Here we show that Smpd3 expression in ATDC5 chondrogenic cells is downregulated by parathyroid hormone-related peptide through transcription factor SOX9. Furthermore, we show that transgenic expression of Smpd3 in the chondrocytes of fro/fro mice corrects the cartilage but not the bone abnormalities. Additionally, we report the generation of Smpd3 flox/flox mice for the tissue-specific inactivation of Smpd3 using the Cre-loxP system. We found that the skeletal phenotype in Smpd3 flox/flox ; Osx-Cre mice, in which the Smpd3 gene is ablated in both late-stage chondrocytes and osteoblasts, closely mimics the skeletal phenotype in fro/fro mice. On the other hand, Smpd3 flox/flox ; Col2a1-Cre mice, in which the Smpd3 gene is knocked out in chondrocytes only, recapitulate the fro/fro mouse cartilage phenotype. This work demonstrates that Smpd3 expression in both chondrocytes and osteoblasts is required for normal endochondral bone development. Sphingomyelin phosphodiesterase 3 (SMPD3) is a lipid-metabolizing enzyme present in the membranes of the endoplasmic reticulum and the inner leaflet of the cell membrane (1). Recently, this enzyme has been identified to be a key regulator of skeletal development (2-6). SMPD3 cleaves sphingomyelin and generates ceramides, a class of lipid second messengers, and phosphocholine, an important intermediate for a number of metabolic pathways (7-9).Currently, there are two reported mouse models that lack functional SMPD3. These mouse models have been extensively used to study the physiological roles of this enzyme. Mice in the first model, the fro/fro mouse model, harbor a recessive mutation called fragilitas ossium (fro). It was generated by chemically inducing a deletion in the Smpd3 gene, leading to a complete loss of SMPD3 enzymatic activity (2). The second model, consisting of Smpd3 Ϫ/Ϫ mice, in which Smpd3 was ablated in all the tissues, was generated by a gene-targeting method (2, 10, 11). Stoffel et al. identified the skeletal abnormalities in Smpd3Ϫ/Ϫ mice to be a form of chondrodysplasia (10, 11). Their study suggested that neuronal SMPD3, through systemic means, regulates skeletal development. On the other hand, Aubin et al. reported that the fro mutation results in osteogenesis and dentinogenesis imperfecta (2). Although the skeletal deformities were somewhat similar in the two mouse models, they were more severe in fro/fro mice than in Smpd3 Ϫ/Ϫ mice. Moreover, fro/fro mice showed bone and tooth mineralization defects, which were not investigated in Smpd3 Ϫ/Ϫ mice (5, 12). The phenotypic discrepancies between these two mouse models demand further investigation of the tissue-specific roles of SMPD3 during skeletogenesis.Ou...

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Roles and regulation of neutral sphingomyelinase-2 in cellular and pathological processes

Cited by 186 publications

References 153 publications

Mycobacterial Infection is Promoted by Neutral Sphingomyelinase 2 Regulating a Signaling Cascade Leading to Activation of β1-Integrin

Mycobacterial Infection is Promoted by Neutral Sphingomyelinase 2 Regulating a Signaling Cascade Leading to Activation of β1-Integrin

Structure of human nSMase2 reveals an interdomain allosteric activation mechanism for ceramide generation

Smpd3 Expression in both Chondrocytes and Osteoblasts Is Required for Normal Endochondral Bone Development

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