A PKC-Sp1 signaling pathway induces early differentiation of human keratinocytes through upregulation of TSG101.
The TSG101 protein has been implicated in multiple biological functions including regulation of gene transcription, vesicular trafficking, cellular growth and differentiation. However, the cellular signals that control TSG101 functions are unclear. Here, we demonstrate that TSG101 is upregulated during keratinocyte differentiation in both human foreskin tissue and reconstructed organotypic skin cultures. In addition, we found that TSG101 siRNA inhibits calcium-induced early differentiation of human foreskin keratinocytes, indicating an essential and downstream role for TSG101 in this process. Furthermore, the PKC agonist TPA promotes expression of TSG101 and keratin 10 in keratinocytes under low calcium conditions, while co-treatment with the PKC inhibitor GF 109203X blocks TPA-induced TSG101 and keratin 10 upregulation. Previous work has established that the TSG101 gene is controlled by a TATA-less promoter that harbors a Sp1-binding site. Here we show that both calcium and TPA activate PKC, stimulate phosphorylation of Sp1, and augment the activity of the TSG101 promoter in a manner dependent on its Sp1-binding site. Release of calcium from intracellular stores with thapsigargin, an endoplasmic reticulum Ca2+-ATPase inhibitor that elevates intracellular free Ca2+ without activating PKC, does not affect Sp1 phosphorylation and TSG101 promoter activity. Taken together, these data suggest that an intracellular calcium store independent PKC-Sp1 signaling pathway induces early keratinocyte differentiation through upregulation of TSG101.
You
Huey-Ling
HL
Department of Biological Sciences, National Sun Yat-Sen University, 70 Lien Hai Road, and Department of Pathology, Chang Gung Memorial Hospital, Kaohsiung, Taiwan 80833, Republic of China.
Eng
Hock-Liew
HL
Hsu
Shih-Fang
SF
Chen
Ching-Mei
CM
Ye
Tzung-Cheng
TC
Liao
Wei-Ting
WT
Huang
Man-Yi
MY
Baer
Richard
R
Cheng
Jiin-Tsuey
JT
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport; D000078404:Epidermal Cells; D004817:Epidermis / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015603:Keratinocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*; D000099177:Tsg101 Protein
D002118:Calcium; D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D007211:Indoles; D008301:Maleimides; D011493:Protein Kinase C; D016329:Sp1 Transcription Factor; D019284:Thapsigargin; D014157:Transcription Factors; D000099177:Tsg101 Protein; C070515:bisindolylmaleimide I