title: Tetraspanins stimulate protein synthesis in myeloma cell lines.
abstract: Intensive protein synthesis is a unique and differential trait of multiple myeloma (MM) cells. Previously we showed that tetraspanin (CD81, CD82) overexpression in MM cell lines attenuated Akt/mTOR cascades, activated UPR, and caused autophagic death, suggesting breach of protein homeostasis. Here, we explored the role of protein synthesis in the tetraspanin-induced MM cell death. Contrary to attenuation of the major metabolic regulator, mTOR we determined elevated steady-state levels of protein in CD81N1/CD82N1 transfected MM lines (RPMI-8226, CAG). Elevated levels of immunoglobulins supported increased protein production in RPMI-8226. Changes in cell morphology consistent with elevated protein synthesis were also determined (cell, nuclei, and nucleoli sizes and ratios). Increased levels of phospho-rpS6 and decreased levels of phospho-AMPK were consistent with increased translation but independent of mTOR. Involvement of p38 and its role in tetraspanin induced translation and cell death were demonstrated. Microarray analyses of tetraspanin transfected MM cell lines revealed activation of protein synthesis signaling cascades and signals implicated in ribosome biogenesis (snoRNAs). Finally, we showed tetraspanins elevated protein synthesis was instrumental to MM cells' death. This work explores and demonstrates that excessive protein translation can be detrimental to MM cell lines and therefore may present a therapeutic target. Proteostasis is particularly important in MM because it integrates the high levels of protein production unique to myeloma cells with critically important microenvironmental cues. We suggest that increasing translation may be the path of least resistance in MM and thus may afford a novel platform for strategically designed therapy.
authors.affiliation: Oncogenetic Laboratory, Meir Medical Center, Kfar Saba, Israel.
authors.forename: Victoria
authors.initials: V
authors.lastname: Zismanov
authors.forename: Liat
authors.initials: L
authors.lastname: Drucker
authors.forename: Oshrat
authors.initials: O
authors.lastname: Attar-Schneider
authors.forename: Shelly Tartakover
authors.initials: ST
authors.lastname: Matalon
authors.forename: Metsada
authors.initials: M
authors.lastname: Pasmanik-Chor
authors.forename: Michael
authors.initials: M
authors.lastname: Lishner
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D017209:Apoptosis; D045744:Cell Line, Tumor; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis; D051861:Kangai-1 Protein / Q000378:metabolism*; D009101:Multiple Myeloma / Q000378:metabolism*; D014176:Protein Biosynthesis; D038601:Ribosomal Protein S6 / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D060225:Tetraspanin 28 / Q000378:metabolism*; D059470:Tetraspanins / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D007136:Immunoglobulins; D051861:Kangai-1 Protein; D038601:Ribosomal Protein S6; D060225:Tetraspanin 28; D059470:Tetraspanins; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases