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Tyrosine phosphorylation of lamin A by Src promotes disassembly of nuclear lamina in interphase.

ABSTRACT: Lamins form the nuclear lamina, which is important for nuclear structure and activity. Although posttranslational modifications, in particular serine phosphorylation, have been shown to be important for structural properties and functions of lamins, little is known about the role of tyrosine phosphorylation in this regard. In this study, we found that the constitutively active Src Y527F mutant caused the disassembly of lamin A/C. We demonstrate that Src directly phosphorylates lamin A mainly at Tyr45 both in vitro and in intact cells. The phosphomimetic Y45D mutant was diffusively distributed in the nucleoplasm and failed to assemble into the nuclear lamina. Depletion of lamin A/C in HeLa cells induced nuclear dysmorphia and genomic instability as well as increased nuclear plasticity for cell migration, all of which were partially restored by re-expression of lamin A, but further promoted by the Y45D mutant. Together, our results reveal a novel mechanism for regulating the assembly of nuclear lamina through Src and suggest that aberrant phosphorylation of lamin A by Src may contribute to nuclear dysmorphia, genomic instability, and nuclear plasticity.

SUBMITTER: Chu CT

PROVIDER: S-EPMC8362257 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The nuclear lamina lines the inner nuclear membrane providing a structural framework for the nucleus. Cellular processes, such as nuclear envelope breakdown during mitosis or nuclear export of large ribonucleoprotein complexes, are functionally linked to the disassembly of the nuclear lamina. In general, lamina disassembly is mediated by phosphorylation, but the precise molecular mechanism is still not completely understood. Recently, we suggested a novel mechanism for lamina disassembly during the nuclear egress of herpesviral capsids which involves the cellular isomerase Pin1. In this study, we focused on mechanistic details of herpesviral nuclear replication to demonstrate the general importance of Pin1 for lamina disassembly. In particular, Ser22-specific lamin phosphorylation consistently generates a Pin1-binding motif in cells infected with human and animal alpha-, beta-, and gammaherpesviruses. Using nuclear magnetic resonance spectroscopy, we showed that binding of Pin1 to a synthetic lamin peptide induces its cis/trans isomerization in vitro. A detailed bioinformatic evaluation strongly suggests that this structural conversion induces large-scale secondary structural changes in the lamin N-terminus. Thus, we concluded that a Pin1-induced conformational change of lamins may represent the molecular trigger responsible for lamina disassembly. Consistent with this concept, pharmacological inhibition of Pin1 activity blocked lamina disassembly in herpesvirus-infected fibroblasts and consequently impaired virus replication. In addition, a phospho-mimetic Ser22Glu lamin mutant was still able to form a regular lamina structure and overexpression of a Ser22-phosphorylating kinase did not induce lamina disassembly in Pin1 knockout cells. Intriguingly, this was observed in absence of herpesvirus infection proposing a broader importance of Pin1 for lamina constitution. Thus, our results suggest a functional model of similar events leading to disassembly of the nuclear lamina in response to herpesviral or inherent cellular stimuli. In essence, Pin1 represents a regulatory effector of lamina disassembly that promotes the nuclear pore-independent egress of herpesviral capsids.

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Tyrosine phosphorylation of lamin A by Src promotes disassembly of nuclear lamina in interphase.

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