BLOC1S2 interacts with the HIPPI protein and sensitizes NCH89 glioblastoma cells to apoptosis.
The HIPPI (HIP-1 protein interactor) protein is a multifunctional protein that is involved in the regulation of apoptosis. The interaction partners of HIPPI include HIP-1 (Huntingtin-interacting protein-1), Apoptin, Homer1c, Rybp/DEDAF, and BAR (bifunctional apoptosis regulator). In search for other binding partners of HIPPI, we performed a yeast two hybrid screen and identified BLOC1S2 (Biogenesis of lysosome-related organelles complex-1 subunit 2) as a novel HIPPI-interacting protein. In co-immunoprecipitation assays, BLOC1S2 specifically associates with HIPPI, but not with HIP-1. To study the expression of BLOC1S2 on the protein level, we generated a mouse monoclonal antibody specific for BLOC1S2 and a multiple tissue array comprising 70 normal and cancer tissue samples of diverse origin. BLOC1S2 protein is widely expressed in normal tissue as well as in malignant tumors with a tendency towards lower expression levels in certain subtypes of tumors. On the subcellular level, BLOC1S2 is expressed in an organellar-like pattern and co-localizes with mitochondria. Over-expression of BLOC1S2 in the presence or absence of HIPPI does not induce apoptosis. However, BLOC1S2 and HIPPI sensitize NCH89 glioblastoma cells to the pro-apoptotic actions of staurosporine and the death ligand TRAIL by enhancing caspase activation, cytochrome c release, and disruption of the mitochondrial membrane potential. Given its interaction with HIPPI and its pro-apoptotic activity, BLOC1S2 might play an important functional role in cancer and neurodegenerative diseases.
Gdynia
Georg
G
Molecular Neuro-Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany.
Lehmann-Koch
Judith
J
Sieber
Sebastian
S
Tagscherer
Katrin E
KE
Fassl
Anne
A
Zentgraf
Hanswalter
H
Matsuzawa
Shu-Ichi
S
Reed
John C
JC
Roth
Wilfried
W
D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D005260:Female; D005909:Glioblastoma / Q000473:pathology*; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000473:pathology; D011485:Protein Binding; D011506:Proteins / Q000502:physiology*; D016415:Sequence Alignment; D019311:Staurosporine / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology; D014018:Tissue Distribution
D048868:Adaptor Proteins, Signal Transducing; C492647:BLOC1S2 protein, human; C499179:IFT57 protein, human; D011506:Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D045304:Cytochromes c; D053148:Caspase 3; D053181:Caspase 8; D019311:Staurosporine