title: Cloning and initial characterization of a new subunit for mammalian serine-palmitoyltransferase.
abstract: Serine-palmitoyltransferase (SPT) catalyzes the rate-limiting step of the de novo synthesis of sphingolipids. SPT is considered to be a heterodimer composed of two subunits, SPTLC1 and SPTLC2. Here we report the identification of a novel, third, SPT subunit (SPTLC3) that shows 68% homology to the SPTLC2 subunit. Quantitative real-time PCR revealed that SPTLC3 expression is highly variable between different human tissues and cell lines. The highest expression was observed in placenta tissue and human trophoblast cell lines. The overexpression of SPTLC3 in Hek293 cells, which otherwise have very little endogenous SPTLC3, led to a 2- to 3-fold increase in cellular SPT activity. Silencing of SPTLC3 expression in HepG2 cells or human trophoblast cells by transfecting SPTLC3-specific siRNA resulted in a significant reduction of cellular SPT activity. The expression of two SPT isoforms could be a cellular mechanism to adjust SPT activity to tissue-specific requirements of sphingolipid synthesis.
authors.affiliation: Institute for Clinical Chemistry, University Hospital Zürich, Rämistrasse 100, CH-8091 Zürich, Switzerland. thorsten.hornemann@usz.ch
authors.forename: Thorsten
authors.initials: T
authors.lastname: Hornemann
authors.forename: Stephane
authors.initials: S
authors.lastname: Richard
authors.forename: Markus F
authors.initials: MF
authors.lastname: Rütti
authors.forename: Yu
authors.initials: Y
authors.lastname: Wei
authors.forename: Arnold
authors.initials: A
authors.lastname: von Eckardstein
mesh_terms: D000217:Acyltransferases / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D051102:Serine C-Palmitoyltransferase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D014327:Trophoblasts / Q000201:enzymology
chemical_list: D018076:DNA, Complementary; D021122:Protein Subunits; D012333:RNA, Messenger; D000217:Acyltransferases; C487784:SPTLC1 protein, human; C495089:SPTLC2 protein, human; C521151:SPTLC3 protein, human; D051102:Serine C-Palmitoyltransferase