Calmodulin regulates transglutaminase 2 cross-linking of huntingtin.
Striatal and cortical intranuclear inclusions and cytoplasmic aggregates of mutant huntingtin are prominent neuropathological hallmarks of Huntington's disease (HD). We demonstrated previously that transglutaminase 2 cross-links mutant huntingtin in cells in culture and demonstrated the presence of transglutaminase-catalyzed cross-links in the HD cortex that colocalize with transglutaminase 2 and huntingtin. Because calmodulin regulates transglutaminase activity in erythrocytes, platelets, and the gizzard, we hypothesized that calmodulin increases cross-linking of huntingtin in the HD brain. We found that calmodulin colocalizes at the confocal level with transglutaminase 2 and with huntingtin in HD intranuclear inclusions. Calmodulin coimmunoprecipitates with transglutaminase 2 and huntingtin in cells transfected with myc-tagged N-terminal huntingtin fragments containing 148 polyglutamine repeats (htt-N63-148Q-myc) and transglutaminase 2 but not in cells transfected with myc-tagged N-terminal huntingtin fragments containing 18 polyglutamine repeats. Our previous studies demonstrated that transfection with both htt-N63-148Q-myc and transglutaminase 2 resulted in cross-linking of mutant huntingtin protein fragments and the formation of insoluble high-molecular-weight aggregates of huntingtin protein fragments. Transfection with transglutaminase 2 and htt-N63-148Q-myc followed by treatment of cells with N-(6-aminohexyl)-1-naphthalenesulfonamide, a calmodulin inhibitor, resulted in a decrease in cross-linked huntingtin. Inhibiting the interaction of calmodulin with transglutaminase and huntingtin protein could decrease cross-linking and diminish huntingtin aggregate formation in the HD brain.
Department of Pharmacology, Loyola University Medical Center, Maywood, Illinois 60153, USA.
Gina M
GM
Zainelli
Christopher A
CA
Ross
Juan C
JC
Troncoso
John K
JK
Fitzgerald
Nancy A
NA
Muma
D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000378:metabolism* / Q000473:pathology; D045586:Intranuclear Inclusion Bodies / Q000378:metabolism / Q000473:pathology; D046911:Macromolecular Substances; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011233:Precipitin Tests; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014162:Transfection; D011503:Transglutaminases / Q000235:genetics / Q000378:metabolism*; D019680:Trinucleotide Repeat Expansion / Q000235:genetics
D002147:Calmodulin; D004791:Enzyme Inhibitors; C086055:HTT protein, human; D000071058:Huntingtin Protein; D046911:Macromolecular Substances; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; D013449:Sulfonamides; C097188:polyglutamine; C034700:N-(6-aminohexyl)-1-naphthalenesulfonamide; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins