A novel human dynactin-associated protein, dynAP, promotes activation of Akt, and ergosterol-related compounds induce dynAP-dependent apoptosis of human cancer cells.
There are several human genes that may encode proteins whose functions remain unknown. To find clues to their functions, we used the mutant yeast defective in Mad2, a component of the spindle checkpoint complex. Phenotypes that were provoked by the expression of a human C18orf26 protein in the mutant yeast encouraged further characterization of this protein in human cells. This protein was designated dynAP (dynactin-associated protein) because of its interaction with dynactin subunits that comprised a microtubule-based motor protein complex. The dynAP is a transmembrane protein localizing to Golgi apparatus and plasma membrane in a microtubule-dependent manner. This protein was expressed in half of human cancer cell lines but barely in normal human fibroblasts tested. The SV40-transformed fibroblasts expressed dynAP. Importantly, the expression of dynAP activated Akt (also known as protein kinase B) by promoting Ser⁴⁷³ phosphorylation required for the full activation, whereas knockdown of dynAP abolished this activation. The ergosterol-related compounds identified by the yeast cell-based high-throughput screen abrogated activation of Akt and induced apoptosis in a dynAP-dependent manner. We propose a possible advantage of dynAP expression in cancer cells; the survival of cancer cells that express dynAP is supported by dynAP-induced activation of Akt, sustaining high rates of proliferation. The inactivation of dynAP by the selected compounds nullifies this advantage, and thereby, the apoptotic machinery is allowed to operate. Taken together, dynAP can be a new target for cancer therapy, and the selected chemicals are useful for developing a new class of anticancer drugs.
Nagahama Institute of Bio-Science and Technology, Shiga 526-0829, Japan.
Tatsuki
T
Kunoh
Takanori
T
Noda
Koichi
K
Koseki
Masayuki
M
Sekigawa
Motoki
M
Takagi
Kazuo
K
Shin-ya
Naoki
N
Goshima
Shun-ichiro
S
Iemura
Tohru
T
Natsume
Shu-ichi
S
Wada
Yukio
Y
Mukai
Shinji
S
Ohta
Ryuzo
R
Sasaki
Tamio
T
Mizukami
D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D018938:Caco-2 Cells; D002478:Cells, Cultured; D004354:Drug Screening Assays, Antitumor; D000072159:Dynactin Complex; D004789:Enzyme Activation; D004875:Ergosterol / Q000031:analogs & derivatives* / Q000494:pharmacology; D045325:HCT116 Cells; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051058:Oncogene Protein v-akt / Q000378:metabolism*; D030781:Organisms, Genetically Modified; D011485:Protein Binding; D013261:Sterols / Q000494:pharmacology*; D015854:Up-Regulation; D015003:Yeasts
C556169:DynAP protein, human; D000072159:Dynactin Complex; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D013261:Sterols; D051058:Oncogene Protein v-akt; D004875:Ergosterol