Characterization of a series of 4-aminoquinolines that stimulate caspase-7 mediated cleavage of TDP-43 and inhibit its function.
Dysfunction of the heterogeneous ribonucleoprotein TAR DNA binding protein 43 (TDP-43) is associated with neurodegeneration in diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Here we examine the effects of a series of 4-aminoquinolines with affinity for TDP-43 upon caspase-7-induced cleavage of TDP-43 and TDP-43 cellular function. These compounds were mixed inhibitors of biotinylated TG6 binding to TDP-43, binding to both free and occupied TDP-43. Incubation of TDP-43 and caspase-7 in the presence of these compounds stimulated caspase-7 mediated cleavage of TDP-43. This effect was antagonized by the oligonucleotide TG12, prevented by denaturing TDP-43, and exhibited a similar relation of structure to function as for the displacement of bt-TG6 binding to TDP-43. In addition, the compounds did not affect caspase-7 enzyme activity. In human neuroglioma H4 cells, these compounds lowered levels of TDP-43 and increased TDP-43 C-terminal fragments via a caspase-dependent mechanism. Subsequent experiments demonstrated that this was due to induction of caspases 3 and 7 leading to increased PARP cleavage in H4 cells with similar rank order of the potency among the compounds tests for displacement of bt-TG6 binding. Exposure to these compounds also reduced HDAC-6, ATG-7, and increased LC3B, consistent with the effects of TDP-43 siRNA described by other investigators. These data suggest that such compounds may be useful biochemical probes to further understand both the normal and pathological functions of TDP-43, and its cleavage and metabolism promoted by caspases.
ALS Biopharma, LLC, Pennsylvania Biotechnology Center, 3805 Old Easton Rd., Doylestown, PA 18902, USA. jcassel@alsbiopharma.com
Joel A
JA
Cassel
Mark E
ME
McDonnell
Venkata
V
Velvadapu
Vyacheslav
V
Andrianov
Allen B
AB
Reitz
D000634:Aminoquinolines / Q000378:metabolism / Q000494:pharmacology*; D000071193:Autophagy-Related Protein 7; D019921:Biotinylation / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D057166:High-Throughput Screening Assays; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects*; D034741:RNA, Small Interfering / Q000235:genetics; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism
D000634:Aminoquinolines; D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D053179:Caspase 7; C433811:HDAC6 protein, human; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes; C001920:4-aminoquinoline