Upregulation of the human alkaline ceramidase 1 and acid ceramidase mediates calcium-induced differentiation of epidermal keratinocytes.
Extracellular calcium (Ca2+(o)) potently induces the growth arrest and differentiation of human epidermal keratinocytes (HEKs). We report that Ca2+(o) markedly upregulates the human alkaline ceramidase 1 (haCER1) in HEKs; and its upregulation mediates the Ca2+(o)-induced growth arrest and differentiation of HEKs. haCER1 is the human ortholog of mouse alkaline ceramidase 1 that we previously identified. haCER1 catalyzed the hydrolysis of very long-chain ceramides to generate sphingosine (SPH). This in vitro activity required Ca2+. Ectopic expression of haCER1 in HEKs decreased the levels of D-e-C(24:1)-ceramide and D-e-C(24:0)-ceramide but elevated the levels of both SPH and its phosphate (S1P), whereas RNA interference-mediated knockdown of haCER1 caused the opposite effects on the levels of these sphingolipids in HEKs. Similar to haCER1 overexpression, Ca2+(o) increased the levels of SPH and S1P, and this was attenuated by haCER1 knockdown. haCER1 knockdown also inhibited the Ca2+(o)-induced growth arrest of HEKs and the Ca2+(o)-induced expression of keratin 1 and involucrin in HEKs. In addition, the acid ceramidase (AC) was also upregulated by Ca2+(o); and its knockdown attenuated the Ca2+(o)-induced expression of keratin 1 and involucrin in HEKs. These results strongly suggest that upregulation of haCER1 and AC mediates the Ca2+(o)-induced growth arrest and differentiation of HEKs by generating SPH and S1P.
Sun
Wei
W
Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, USA.
Xu
Ruijuan
R
Hu
Wei
W
Jin
Junfei
J
Crellin
Heather A
HA
Bielawski
Jacek
J
Szulc
Zdzislaw M
ZM
Thiers
Bruce H
BH
Obeid
Lina M
LM
Mao
Cungui
C
D055573:Acid Ceramidase; D055574:Alkaline Ceramidase; D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D055572:Ceramidases; D002518:Ceramides / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000201:enzymology; D000078404:Epidermal Cells; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D002517:Galactosylgalactosylglucosylceramidase / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000201:enzymology*; D034741:RNA, Small Interfering; D013379:Substrate Specificity; D015854:Up-Regulation / Q000502:physiology
D002518:Ceramides; D005231:Fatty Acids, Unsaturated; D034741:RNA, Small Interfering; D004815:Epidermal Growth Factor; D002517:Galactosylgalactosylglucosylceramidase; D000581:Amidohydrolases; C526750:ACER1 protein, human; C526755:ACER2 protein, human; C526693:ASAH1 protein, human; C526753:Acer1 protein, mouse; D055573:Acid Ceramidase; D055574:Alkaline Ceramidase; C526734:Asah1 protein, mouse; D055572:Ceramidases; D002118:Calcium