title: Proapoptotic Requirement of Ribosomal Protein L11 in Ribosomal Stress-Challenged Cortical Neurons.
abstract: While impaired ribosomal biogenesis is observed in neurodegenerative diseases, its pathogenic contributions are not clear. For instance, it is well established that in rodent neurons, genetic inhibition of RNA-polymerase 1 that transcribes rRNA results in structural disruption of the nucleolus, neuronal apoptosis, and neurodegeneration. However, in most neurodegenerative diseases, nucleolar morphology is unaffected. It is reported here that in primary cortical neurons from newborn rats, inhibition of ribosomal biogenesis by shRNA-mediated knockdowns of several ribosomal proteins including S6, S14, or L4 resulted in p53-mediated apoptosis despite absence of structural disruption of the nucleolus. Conversely, knockdown of the RP L11, which in nonneuronal systems mediates p53 activation downstream of ribosomal stress, protected neurons against inhibition of ribosomal biogenesis but not staurosporine. Moreover, overexpression of L11 enhanced p53-driven transcription and increased neuronal apoptosis. In addition, inhibition of p53, or L11 knockdown, blocked apoptosis in response to the RNA analog 5-fluorouridine which perturbed nucleolar structure, inhibited ribosomal synthesis, and activated p53. Although the DNA double-strand break (DSB) inducer etoposide activated p53, nucleolar structure appeared intact. However, by activating the DNA damage response kinase ATM, etoposide increased 47S pre-rRNA levels, and enhanced nucleolar accumulation of nascent RNA, suggesting slower rRNA processing and/or increased Pol1 activity. In addition, shL11 reduced etoposide-induced apoptosis. Therefore, seemingly normal morphology of the neuronal nucleolus does not exclude presence of ribosomal stress. Conversely, targeting the ribosomal stress-specific signaling mediators including L11 offers a novel approach to uncover neurodegenerative contributions of deregulated ribosomal synthesis as exemplified in DSB-challenged neurons.
authors.affiliation: KY Spinal Cord Injury Research Center and the Department of Neurological Surgery, University of Louisville, 511 S. Floyd St., MDR616, Louisville, KY, 40292, USA.
authors.forename: Lukasz P
authors.initials: LP
authors.lastname: Slomnicki
authors.affiliation: KY Spinal Cord Injury Research Center and the Department of Neurological Surgery, University of Louisville, 511 S. Floyd St., MDR616, Louisville, KY, 40292, USA.|Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY, 40292, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Hallgren
authors.affiliation: KY Spinal Cord Injury Research Center and the Department of Neurological Surgery, University of Louisville, 511 S. Floyd St., MDR616, Louisville, KY, 40292, USA.
authors.forename: Aruna
authors.initials: A
authors.lastname: Vashishta
authors.affiliation: KY Spinal Cord Injury Research Center and the Department of Neurological Surgery, University of Louisville, 511 S. Floyd St., MDR616, Louisville, KY, 40292, USA.
authors.forename: Scott C
authors.initials: SC
authors.lastname: Smith
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, KY, 40292, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Ellis
authors.affiliation: KY Spinal Cord Injury Research Center and the Department of Neurological Surgery, University of Louisville, 511 S. Floyd St., MDR616, Louisville, KY, 40292, USA. michal.hetman@louisville.edu.|Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY, 40292, USA. michal.hetman@louisville.edu.
authors.forename: Michal
authors.initials: M
authors.lastname: Hetman
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D002466:Cell Nucleolus / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000473:pathology*; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D005472:Fluorouracil / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D017207:Rats, Sprague-Dawley; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D012269:Ribosomal Proteins; D016159:Tumor Suppressor Protein p53; C027624:ribosomal protein L11; D005047:Etoposide; D064007:Ataxia Telangiectasia Mutated Proteins; D005472:Fluorouracil
keywords: Apoptosis; DNA damage; Neurons; Nucleolus; Ribosomal proteins; p53