Expression and distribution of HuR during ATP depletion and recovery in proximal tubule cells.
Human antigen R (HuR) is a nucleocytoplasmic shuttling protein that binds to and stabilizes mRNAs containing adenine- and uridine-rich elements. Under normal growth conditions, the bulk of HuR is maintained in the nucleus, but under conditions of cell stress, HuR may become more prevalent in the cytosol, where it can stabilize mRNA and regulate gene expression. We have studied the behavior of HuR in LLC-PK1 proximal tubule cells subjected to ATP depletion and recovery. ATP depletion resulted in detectable net movement of HuR out of the nucleus, followed by net movement of HuR back into the nucleus on reversion to normal growth medium. In addition, HuR protein levels increased during energy depletion. This increase was inhibited by cycloheximide and was independent of HuR mRNA levels, since no change was noted in the quantity of HuR transcript. In contrast, recovery in normal growth medium resulted in increased HuR mRNA, while protein levels decreased to baseline. This suggested a mechanism by which previously injured cells maintained normal levels of HuR but were primed to rapidly translate increased amounts of protein on subsequent insults. Indeed, a second round of ATP depletion resulted in heightened HuR protein translation at a rate more rapid than during the first insult. Additionally, the second insult produced increased HuR levels in the cytoplasm while still maintaining high amounts in the nucleus, indicating that nuclear export may not be required on subsequent insults. These results suggest a role for HuR in protecting kidney epithelia from injury during ischemic stress.
Jeyaraj
Selvi C
SC
Department of Physiology and Cell Biology, The Ohio State University, 1645 Neil Ave., Columbus, OH 43210, USA.
Dakhlallah
Duaa
D
Hill
Stephanie R
SR
Lee
Beth S
BS
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics* / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D004734:Energy Metabolism / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D007511:Ischemia / Q000378:metabolism / Q000503:physiopathology*; D019194:Ischemic Preconditioning / Q000379:methods; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D018374:LLC-PK1 Cells; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D013552:Swine
D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000255:Adenosine Triphosphate