UVB irradiation up-regulates serine palmitoyltransferase in cultured human keratinocytes

Angela M. Farrell, Yoshikazu Uchida, M. Marek Nagiec, Ian R. Harris, Robert C. Dickson, Peter M. Elias, Walter M. Holleran

Research output: Contribution to journalArticlepeer-review

86 Scopus citations

Abstract

The enzyme serine palmitoyltransferase (SPT; EC 2.3.1.50), which catalyzes the first committed and rate-limiting step in sphingolipid synthesis, is up-regulated in the epidermis as part of the homeostatic repair in response to permeability barrier perturbation. Moreover, UVB exposure, which also perturbs the barrier, up-regulates sphingolipid synthesis, but the basis for this increase is not known. The recent isolation of cDNAs for SPT (i.e., LCB1 and LCB2) allow molecular regulation studies to be performed. Therefore, we determined whether UVB exposure alters mRNA, protein, or activity levels for SPT in cultured human keratinocytes (CHKs) as a mechanism for regulation of epidermal sphingolipid synthesis. In CHK, transcripts for both LCB1 (3.0 kb) and LCB2 (2.3 kb) are evident by Northern blot analysis, and UVB exposure (23 mJ/cm2) induces a delayed 1.8 to 3.3-fold increase in LCB2 mRNA levels (P < 0.01) 48 h after treatment versus non-irradiated control cells. In contrast, neither LCB1 nor a second LCB2 transcript (8.0 kb) changed significantly. Likewise, Lcb2 protein levels (by Western blot analysis), as well as SPT activity, increase in parallel with the increased LCB2 mRNA. Finally, incorporation of [14C]-acetate into sphingolipids was increased significantly 48 h after UVB treatment. Together, these results demonstrate that CHKs respond to UVB by increasing sphingolipid synthesis, primarily through increases in both LCB2 mRNA and protein levels, leading to increased SPT activity. These results demonstrate one mechanism (UVB) whereby SPT is regulated at the molecular level, and suggest further that epidermis up-regulates sphingolipid synthesis at both the mRNA and protein levels in response to UVB. - Farrell, A. M., Y. Uchida, M. M. Nagiec, I. R. Harris, R. C. Dickson, P. M. Elias, and W. M. Holleran. UVB irradiation up-regulates serine palmitoyltransferase in cultured human keratinocytes.

Original languageEnglish
Pages (from-to)2031-2038
Number of pages8
JournalJournal of Lipid Research
Volume39
Issue number10
StatePublished - Oct 1998

Keywords

  • Barrier
  • Ceramides
  • Epidermis
  • Keratinocytes
  • Seri ne palmitoyltransferase
  • Skin
  • Sphingolipids
  • Sphingosine
  • UVB

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Cell Biology

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