title: Histological analyses by matrix-assisted laser desorption/ionization-imaging mass spectrometry reveal differential localization of sphingomyelin molecular species regulated by particular ceramide synthase in mouse brains.
abstract: Sphingomyelin (SM) is synthesized by SM synthase (SMS) from ceramide (Cer). SM regulates signaling pathways and maintains organ structure. SM comprises a sphingoid base and differing lengths of acyl-chains, but the importance of its various forms and regulatory synthases is not known. It has been reported that Cer synthase (CerS) has restricted substrate specificity, whereas SMS has no specificity for different lengths of acyl-chains. We hypothesized that the distribution of each SM molecular species was regulated by expression of the CerS family. Thus, we compared the distribution of SM species and CerS mRNA expression using molecular imaging. Spatial distribution of each SM molecular species was investigated using ultra-high-resolution imaging mass spectrometry (IMS). IMS revealed that distribution of SM molecular species varied according to the lengths of acyl-chains found in each brain section. Furthermore, a combination study using in situ hybridization and IMS revealed the spatial expression of CerS1 to be associated with the localization of SM (d18:1/18:0) in cell body-rich gray matter, and CerS2 to be associated with SM (d18:1/24:1) in myelin-rich white matter. Our study is the first comparison of spatial distribution between SM molecular species and CerS isoforms, and revealed their distinct association in the brain. These observations were demonstrated by suppression of CerS2 using siRNA in HepG2 cells; that is, siRNA for CerS2 specifically decreased C22 very long-chain fatty acid (VLCFA)- and C24 VLCFA-containing SMs. Thus, histological analyses of SM species by IMS could be a useful approach to consider their molecular function and regulative mechanism.
authors.affiliation: Shionogi Innovation Center for Drug Discovery, Discovery Research Laboratory for Innovative Frontier Medicines, Shionogi & Co., Ltd., Sapporo 001-0021, Japan; Department of Integrated Molecular Imaging, Graduate School of Medicine, Hokkaido University, Sapporo 060-0815, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Sugimoto
authors.affiliation: Central Institute of Isotope Science, Hokkaido University, Sapporo 060-0815, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Shionogi Innovation Center for Drug Discovery, Discovery Research Laboratory for Innovative Frontier Medicines, Shionogi & Co., Ltd., Sapporo 001-0021, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoshioka
authors.affiliation: Shionogi Innovation Center for Drug Discovery, Discovery Research Laboratory for Innovative Frontier Medicines, Shionogi & Co., Ltd., Sapporo 001-0021, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Wakabayashi
authors.affiliation: Shionogi Pharmacological Research Center, Research Laboratory for Development, Shionogi & Co., Ltd., Osaka 561-0825, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Shionogi Innovation Center for Drug Discovery, Discovery Research Laboratory for Innovative Frontier Medicines, Shionogi & Co., Ltd., Sapporo 001-0021, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Higashino
authors.affiliation: Shionogi Innovation Center for Drug Discovery, Discovery Research Laboratory for Innovative Frontier Medicines, Shionogi & Co., Ltd., Sapporo 001-0021, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Numata
authors.affiliation: Department of Biomembrane and Biofunctional Chemistry, Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Sakai
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Science, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Kihara
authors.affiliation: Department of Biomembrane and Biofunctional Chemistry, Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Igarashi
authors.affiliation: Department of Integrated Molecular Imaging, Graduate School of Medicine, Hokkaido University, Sapporo 060-0815, Japan; Central Institute of Isotope Science, Hokkaido University, Sapporo 060-0815, Japan. Electronic address: kuge@ric.hokudai.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kuge
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry / Q000502:physiology; D056945:Hep G2 Cells; D006801:Humans; D008297:Male; D051379:Mice; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013109:Sphingomyelins / Q000096:biosynthesis*; D051049:Sphingosine N-Acyltransferase / Q000378:metabolism*
chemical_list: D013109:Sphingomyelins; C580723:Cers2 protein, mouse; D051049:Sphingosine N-Acyltransferase
keywords: Ceramide synthase; Fourier transform ion cyclotron resonance; Imaging mass spectrometry; Sphingomyelin; Very long-chain fatty acid