RESUMO
Dendritic cell-specific transmembrane protein (DC-STAMP) has been first identified as an EST in a cDNA library of human monocyte-derived dendritic cells (DC). DC-STAMP is a multimembrane spanning protein that has been implicated in skewing haematopoietic differentiation of bone marrow cells towards the myeloid lineage, and in cell fusion during osteoclastogenesis and giant cell formation. To gain molecular insight in how DC-STAMP exerts its function, DC-STAMP interacting proteins were identified in a yeast-2-hybrid analysis. Herein, we report that amplified in osteosarcoma 9 (OS9) physically interacts with DC-STAMP, and that both proteins colocalize in the endoplasmic reticulum in various cell lines, including immature DC. OS9 has previously been implicated in ER-to-Golgi transport and transcription factor turnover. Interestingly, we now demonstrate that toll-like receptor (TLR)-induced maturation of DC leads to the translocation of DC-STAMP from the ER to the Golgi while OS9 localization is unaffected. Applying TLR-expressing CHO cells we could confirm ER-to-Golgi translocation of DC-STAMP following TLR stimulation and demonstrated that the DC-STAMP/OS9 interaction is involved in this process. Collectively, the data indicate that OS9 is critically involved in the modulation of ER-to-Golgi transport of DC-STAMP in response to TLR triggering, suggesting a novel role for OS9 in myeloid differentiation and cell fusion.
Assuntos
Células Dendríticas/metabolismo , Retículo Endoplasmático/imunologia , Proteínas de Membrana/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Animais , Células CHO , Cricetinae , Cricetulus , Células Dendríticas/citologia , Células Dendríticas/imunologia , Retículo Endoplasmático/metabolismo , Humanos , Lectinas , Proteínas de Membrana/química , Proteínas de Membrana/genética , Proteínas de Membrana/imunologia , Proteínas Mutantes/metabolismo , Proteínas de Neoplasias/química , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/imunologia , Transporte Proteico/fisiologia , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Proteínas Recombinantes de Fusão/metabolismo , Deleção de Sequência/genética , Deleção de Sequência/imunologia , Transdução de Sinais/imunologia , Receptores Toll-Like/imunologia , Receptores Toll-Like/metabolismoRESUMO
Dendritic cells (DCs) are the professional antigen-presenting cells (APC) which efficiently prime the immune response or induce tolerance. We recently identified Dendritic Cell Specific TrAnsMembrane Protein (DC-STAMP), a novel 470 amino acid protein preferentially expressed by dendritic cells. Previously we demonstrated that DC-STAMP re-localizes towards the Golgi upon DC maturation. To identify proteins that interact with DC-STAMP, a yeast-2-hybrid analysis was performed. Here, we report a physically interacting partner of DC-STAMP in the endoplasmic reticulum (ER), called LUMAN (also known as CREB3 or LZIP). LUMAN was previously described as an ER-resident transcription factor with unknown function. It is activated in a process called regulated intramembrane proteolysis (RIP), which involves translocation to the Golgi and subsequent proteolytic cleavage. The proteolytically activated form of the protein then translocates to the nucleus. Our data indicate that DC-STAMP plays an important role in the modulation of LUMAN activation. Moreover, we demonstrate that LUMAN is endogenously expressed by DC and becomes activated by RIP upon DC maturation induced by various different stimuli. These data define LUMAN/DC-STAMP as a novel regulatory circuit in DC.