Internalization of REIC/Dkk-3 protein by induced pluripotent stem cell-derived embryoid bodies and extra-embryonic tissues.
REIC/Dkk-3 was first identified as a down-regulated gene in a number of human immortalized cells and human tumor-derived cell lines. Overexpression of the REIC/Dkk-3 gene using an adenovirus vector (Ad-REIC) has showed a potent selective therapeutic effect on various human cancers through induction of ER stress. Furthermore, we recently showed that Ad-REIC has an indirect host-mediated anti-tumor activity by induction of IL-7. However, the physiological function of REIC/Dkk-3 is still unclear. As a first step to study the possible receptor(s) for secreted REIC/Dkk-3, we analyzed the internalization of Cy3-labeled recombinant REIC/Dkk-3 protein. Among the cell lines screened, mouse induced pluripotent stem (iPS) cells showed a unique pattern of internalization. The internalization was observed in peripheral cells of spherical colonies formed spontaneously, but not in undifferentiated iPS cells. When we analyzed embryoid bodies (EBs) derived from iPS cells, REIC/Dkk-3 protein was internalized specifically by differentiated cells located at the periphery of EBs. Interestingly, Dkk-1 was internalized by undifferentiated cells at the center of the EBs. When developmental tissue was analyzed, internalization of REIC/Dkk-3 protein was strictly limited to extra-embryonic tissue, such as the trophectoderm layer of 4.5 days post-coitus (dpc) blastocysts and the chorionic membrane at 16.5 dpc. The mechanism of the internalization was confirmed to be endocytosis. These findings will contribute to knowledge on the interaction of REIC/Dkk-3 with a possible receptor(s).
Department of Cell Biology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama, Japan.
Ken
K
Kataoka
Masakiyo
M
Sakaguchi
Kun Peng
KP
Li
Chika
C
Taketa
Ken-Ichi
K
Yamamoto
Gang
G
Du
Hiroaki
H
Funahashi
Hitoshi
H
Murata
Nam-Ho
NH
Huh
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002232:Carbocyanines / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D018925:Chemokines; D058732:Embryoid Bodies / Q000166:cytology / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D002232:Carbocyanines; D018925:Chemokines; C498624:DKK3 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; C089187:cyanine dye 3