title: Increased keratinocyte proliferation initiated through downregulation of desmoplakin by RNA interference.
abstract: The intercellular adhesive junction desmosomes are essential for the maintenance of tissue structure and integrity in skin. Desmoplakin (Dp) is a major obligate plaque protein which plays a fundamental role in anchoring intermediate filaments to desmosomal cadherins. Evidence from hereditary human disease caused by mutations in the gene encoding Dp, e.g. Dp haploinsufficiency, suggests that alterations in Dp expression result not only in the disruption of tissue structure and integrity but also could evoke changes in keratinocyte proliferation. We have used transient RNA interference (RNAi) to downregulate Dp specifically in HaCaT keratinocytes. We showed that this Dp downregulation also caused reduced expression of several other desmosomal proteins. Increased cell proliferation and enhanced G(1)-to-S-phase entry in the cell cycle, as monitored by colonial cellular density and BrdU incorporation, were seen in Dp RNAi-treated cells. These proliferative changes were associated with elevated phospho-ERK1/2 and phospho-Akt levels. Furthermore, this increase in phospho-ERK/1/2 and phospho-Akt levels was sustained in Dp RNAi-treated cells at confluence whereas in control cells there was a significant reduction in phosphorylation of ERK1/2. This study indicates that Dp may participate in the regulation of keratinocyte cell proliferation by, in part at least, regulating cell cycle progression.
authors.affiliation: Centre for Tumour Biology, Institute of Cancer and CR-UK Clinical Centre, Barts and The London, Queen Mary's School of Medicine and Dentistry, John Vane Science Centre, Charterhouse Square, London, UK. hong.wan@cancer.org.uk
authors.forename: Hong
authors.initials: H
authors.lastname: Wan
authors.forename: Andrew P
authors.initials: AP
authors.lastname: South
authors.forename: Ian R
authors.initials: IR
authors.lastname: Hart
mesh_terms: D001973:Bromodeoxyuridine / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics*; D049109:Cell Proliferation / Q000187:drug effects; D051180:Desmoplakins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D051181:Desmosomal Cadherins / Q000378:metabolism; D003896:Desmosomes / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D011498:Protein Precursors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology
chemical_list: D051180:Desmoplakins; D051181:Desmosomal Cadherins; D011498:Protein Precursors; D034741:RNA, Small Interfering; C032253:involucrin; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D001973:Bromodeoxyuridine