| RRC ID |
44634
|
| Author |
den Engelsman J, van de Schootbrugge C, Yong J, Pruijn GJ, Boelens WC.
|
| Title |
Pseudophosphorylated αB-crystallin is a nuclear chaperone imported into the nucleus with help of the SMN complex.
|
| Journal |
PLoS One
|
| Abstract |
The human small heat shock protein αB-crystallin (HspB5) is a molecular chaperone which is mainly localized in the cytoplasm. A small fraction can also be found in nuclear speckles, of which the localization is mediated by successional phosphorylation at Ser-59 and Ser-45. αB-crystallin does not contain a canonical nuclear localization signal sequence and the mechanism by which αB-crystallin is imported into the nucleus is not known. Here we show that after heat shock pseudophosphorylated αB-crystallin mutant αB-STD, in which all three phosphorylatable serine residues (Ser-19, Ser-45 and Ser-59) were replaced by negatively charged aspartate residues, is released from the nuclear speckles. This allows αB-crystallin to chaperone proteins in the nucleoplasm, as shown by the ability of αB-STD to restore nuclear firefly luciferase activity after a heat shock. With the help of a yeast two-hybrid screen we found that αB-crystallin can interact with the C-terminal part of Gemin3 and confirmed this interaction by co-immunoprecipitation. Gemin3 is a component of the SMN complex, which is involved in the assembly and nuclear import of U-snRNPs. Knockdown of Gemin3 in an in situ nuclear import assay strongly reduced the accumulation of αB-STD in nuclear speckles. Furthermore, depletion of SMN inhibited nuclear import of fluorescently labeled recombinant αB-STD in an in vitro nuclear import assay, which could be restored by the addition of purified SMN complex. These results show that the SMN-complex facilitates the accumulation of hyperphosphorylated αB-crystallin in nuclear speckles, thereby creating a chaperone depot enabling a rapid chaperone function in the nucleus in response to stress.
|
| Volume |
8(9)
|
| Pages |
e73489
|
| Published |
2013-1-1
|
| DOI |
10.1371/journal.pone.0073489
|
| PII |
PONE-D-13-21703
|
| PMID |
24023879
|
| PMC |
PMC3762725
|
| MeSH |
Active Transport, Cell Nucleus
Cell Nucleus / metabolism*
DEAD Box Protein 20 / metabolism
HeLa Cells
Humans
Phosphorylation
SMN Complex Proteins / metabolism*
alpha-Crystallin B Chain / metabolism*
|
| IF |
2.74
|
| Times Cited |
13
|
|
WOS Category
|
BIOCHEMISTRY & MOLECULAR BIOLOGY
|
| Resource |
| Human and Animal Cells |
anti-αB-crystallin(RCB1304) |
