A novel role for Niemann-Pick disease type 2C protein in papillae formation.
BACKGROUND
Despite the presence of papillary structures and papillary tumors in humans, the mechanism of papillae formation is unknown. We describe herein a novel role for Niemann-Pick disease type 2C (NPC2) protein, a cholesterol binding protein in the lysosome, in papillae formation.


RESULTS
We examined NPC2 protein expression in surgical samples of papillary tissues by immunohistochemical stain, and all papillary tissues expressed NPC2 protein in the epithelium. To examine our hypothesis of NPC2 protein-mediated papillae formation, we carried out xenograft experiments using wild H460 cells (large cell lung carcinoma cell line) that constitutively expressed abundant NPC2 protein and NPC2 protein-depleted H460 cells by NPC2 shRNA. The xenografts of wild H460 cells and empty shRNA vector cells showed distinct papillae formation, whereas NPC2 protein-depleted H460 cells displayed markedly reduced or no papillae. Since all papillary tissues have open spaces we examined whether NPC2 protein might also contribute to the creation of open spaces. The TUNEL assay in the xenografts of wild and empty shRNA vector H460 cells showed massive cell death, and NPC2 protein-depleted cells displayed minimal cell death. Measurement of caspase 3/7 activities in cultured H460 cells supported NPC2 protein-mediated apoptotic cell death. The presence of excess NPC2 protein, however, did not always produce papillae as seen in the xenografts of CHO cells that were stably transfected with NPC2.


CONCLUSIONS
The NPC2 protein of certain cells forms papillae coupled with apoptosis that creates open space. This protein may have future applications to modulate papillae formation and papillary growth in tumor tissues.
Endocrinology and Diabetes Division, Department of Medicine, Veterans Affairs Greater Los Angeles Health Care System, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America. msugawar@ucla.edu
Masahiro
M
Sugawara
Hidemi
H
Ohye
Chisato
C
Tomoda
Takahiko
T
Kogai
Yoshimasa
Y
Kamata
Gholam H
GH
Pezeshkpour
Farhad
F
Moatamed
D000818:Animals; D017209:Apoptosis; D016466:CHO Cells; D002352:Carrier Proteins / Q000032:analysis / Q000502:physiology*; D045744:Cell Line, Tumor; D022081:Cell Surface Extensions / Q000737:chemistry / Q000473:pathology*; D006224:Cricetinae; D003412:Cricetulus; D004848:Epithelium / Q000737:chemistry; D006023:Glycoproteins / Q000032:analysis / Q000172:deficiency / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D009542:Niemann-Pick Diseases / Q000473:pathology*; D014162:Transfection; D014183:Transplantation, Heterologous; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D006023:Glycoproteins; C104585:NPC2 protein, human; D033921:Vesicular Transport Proteins
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