title: Methyl-beta-cyclodextrin suppresses hyaluronan synthesis by down-regulation of hyaluronan synthase 2 through inhibition of Akt.
abstract: Hyaluronan synthases (HAS1-3) are integral plasma membrane proteins that synthesize hyaluronan, a cell surface and extracellular matrix polysaccharide necessary for many biological processes. It has been shown that HAS is partly localized in cholesterol-rich lipid rafts of MCF-7 cells, and cholesterol depletion with methyl-beta-cyclodextrin (MbetaCD) suppresses hyaluronan secretion in smooth muscle cells. However, the mechanism by which cholesterol depletion inhibits hyaluronan production has remained unknown. We found that cholesterol depletion from MCF-7 cells by MbetaCD inhibits synthesis but does not decrease the molecular mass of hyaluronan, suggesting no major influence on HAS stability in the membrane. The inhibition of hyaluronan synthesis was not due to the availability of HAS substrates UDP-GlcUA and UDP-GlcNAc. Instead, MbetaCD specifically down-regulated the expression of HAS2 but not HAS1 or HAS3. Screening of signaling proteins after MbetaCD treatment revealed that phosphorylation of Akt and its downstream target p70S6 kinase, both members of phosphoinositide 3-kinase-Akt pathway, were inhibited. Inhibitors of this pathway suppressed hyaluronan synthesis and HAS2 expression in MCF-7 cells, suggesting that the reduced hyaluronan synthesis by MbetaCD is due to down-regulation of HAS2, mediated by the phosphoinositide 3-kinase-Akt-mTOR-p70S6K pathway.
authors.affiliation: Institute of Biomedicine, Anatomy, University of Eastern Finland, FIN-70211 Kuopio, Finland. anne.kultti@uef.fi
authors.forename: Anne
authors.initials: A
authors.lastname: Kultti
authors.forename: Riikka
authors.initials: R
authors.lastname: Kärnä
authors.forename: Kirsi
authors.initials: K
authors.lastname: Rilla
authors.forename: Pertti
authors.initials: P
authors.lastname: Nurminen
authors.forename: Elina
authors.initials: E
authors.lastname: Koli
authors.forename: Katri M
authors.initials: KM
authors.lastname: Makkonen
authors.forename: Jutong
authors.initials: J
authors.lastname: Si
authors.forename: Markku I
authors.initials: MI
authors.lastname: Tammi
authors.forename: Raija H
authors.initials: RH
authors.lastname: Tammi
mesh_terms: D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D014453:Glucuronosyltransferase / Q000235:genetics*; D006801:Humans; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000096:biosynthesis* / Q000737:chemistry; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D047392:beta-Cyclodextrins / Q000494:pharmacology*
chemical_list: D012333:RNA, Messenger; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D006820:Hyaluronic Acid; D002784:Cholesterol; D014453:Glucuronosyltransferase; C101754:HAS2 protein, human; D000076002:Hyaluronan Synthases; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa