Geldanamycin promotes nuclear localisation and clearance of PHOX2B misfolded proteins containing polyalanine expansions.
Polyalanine expansions in the PHOX2B gene have been detected in the vast majority of patients affected with congenital central hypoventilation syndrome, a neurocristopathy characterized by absence of adequate control of breathing, especially during sleep, with decreased sensitivity to hypoxia and hypercapnia. The correlation between length of the alanine expanded tracts and severity of congenital central hypoventilation syndrome respiratory phenotype has been confirmed by length-dependent cytoplasmic PHOX2B retention with formation of aggregates. To deepen into the molecular mechanisms mediating the effects of PHOX2B polyalanine expansions, we have set up experiments aimed at assessing the fate of cells characterized by PHOX2B polyalanine aggregates. In particular, we have observed that activation of the heat shock response by the drug geldanamycin is efficient both in preventing formation and in inducing clearance of PHOX2B pre-formed polyalanine aggregates in COS-7 cells expressing PHOX2B-GFP fused proteins, and ultimately also in rescuing the PHOX2B ability to transactivate the Dopamine-beta-Hydroxilase promoter. In addition, we have demonstrated elimination of PHOX2B mutant proteins by the proteasome and autophagy, two cellular mechanisms already been involved in the clearance of proteins containing expanded polyglutamine and polyalanine tracts. Moreover, our data suggest that geldanamycin effects on PHOX2B aggregates may be also mediated by the proteasome pathway. Finally, analysis of cellular toxicity due to polyalanine aggregates has confirmed the occurrence of cell apoptosis consequent to expression of PHOX2B carrying the longest expanded alanine tract and shown that geldanamycin can delay cell progression toward the most advanced apoptotic stages.
Bachetti
Tiziana
T
Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, Largo G. Gaslini 5, 16148 Genova, Italy. tiziana.bachetti@tin.it
Bocca
Paola
P
Borghini
Silvia
S
Matera
Ivana
I
Prigione
Ignazia
I
Ravazzolo
Roberto
R
Ceccherini
Isabella
I
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D001343:Autophagy; D016227:Benzoquinones / Q000494:pharmacology* / Q000633:toxicity; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004299:Dopamine beta-Hydroxylase / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology* / Q000633:toxicity; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017510:Protein Folding; D021381:Protein Transport / Q000187:drug effects; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection; D019680:Trinucleotide Repeat Expansion; D025801:Ubiquitin / Q000378:metabolism
D016227:Benzoquinones; D018398:Homeodomain Proteins; D047029:Lactams, Macrocyclic; C109220:NBPhox protein; D010455:Peptides; D014157:Transcription Factors; D025801:Ubiquitin; C019529:polyalanine; D004299:Dopamine beta-Hydroxylase; D046988:Proteasome Endopeptidase Complex; C001277:geldanamycin