Regulating Set-β's Subcellular Localization Toggles Its Function between Inhibiting and Promoting Axon Growth and Regeneration.
The failure of the CNS neurons to regenerate axons after injury or stroke is a major clinical problem. Transcriptional regulators like Set-β are well positioned to regulate intrinsic axon regeneration capacity, which declines developmentally in maturing CNS neurons. Set-β also functions at cellular membranes and its subcellular localization is disrupted in Alzheimer's disease, but many of its biological mechanisms have not been explored in neurons. We found that Set-β was upregulated postnatally in CNS neurons, and was primarily localized to the nucleus but was also detected in the cytoplasm and adjacent to the plasma membrane. Remarkably, nuclear Set-β suppressed, whereas Set-β localized to cytoplasmic membranes promoted neurite growth in rodent retinal ganglion cells and hippocampal neurons. Mimicking serine 9 phosphorylation, as found in Alzheimer's disease brains, delayed nuclear import and furthermore blocked the ability of nuclear Set-β to suppress neurite growth. We also present data on gene regulation and protein binding partner recruitment by Set-β in primary neurons, raising the hypothesis that nuclear Set-β may preferentially regulate gene expression whereas Set-β at cytoplasmic membranes may regulate unique cofactors, including PP2A, which we show also regulates axon growth in vitro. Finally, increasing recruitment of Set-β to cellular membranes promoted adult rat optic nerve axon regeneration after injury in vivo. Thus, Set-β differentially regulates axon growth and regeneration depending on subcellular localization and phosphorylation.
Neuroscience Program, Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101, JLGoldberg@ucsd.edu Ephraim.Trakhtenberg@childrens.harvard.edu.
Ephraim F
EF
Trakhtenberg
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101, Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan 48201, and.
Yan
Y
Wang
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101, Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan 48201, and.
Melina I
MI
Morkin
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101.
Stephanie G
SG
Fernandez
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101.
Gregory M
GM
Mlacker
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101.
Jesse M
JM
Shechter
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101.
Xiongfei
X
Liu
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101.
Karan H
KH
Patel
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101.
Allison
A
Lapins
Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101.
Steven
S
Yang
Genomatix Software, Ann Arbor, Michigan 48108, Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan 48201, and.
Susan M
SM
Dombrowski
Neuroscience Program, Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, Miller School of Medicine, Miami, Florida 33101, Shiley Eye Center, University of California San Diego, La Jolla, California 92093 JLGoldberg@ucsd.edu Ephraim.Trakhtenberg@childrens.harvard.edu.
Jeffrey L
JL
Goldberg
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004622:Embryo, Mammalian; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D009416:Nerve Regeneration / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000648:ultrastructure*; D020221:Optic Nerve Injuries / Q000473:pathology / Q000503:physiopathology*; D035463:Pol1 Transcription Initiation Complex Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology
D009419:Nerve Tissue Proteins; D035463:Pol1 Transcription Initiation Complex Proteins; D049452:Green Fluorescent Proteins