Lamin A Ser404 is a nuclear target of Akt phosphorylation in C2C12 cells.

Abstract

Akt/PKB is a central activator of multiple signaling pathways coupled with a large number of stimuli. Although both localization and activity of Akt in the nuclear compartment are well-documented, most Akt substrates identified so far are located in the cytoplasm, while nuclear substrates have remained elusive. A proteomic-based search for nuclear substrates of Akt was undertaken, exploiting 2D-electrophoresis/MS in combination with an anti-Akt phosphosubstrate antibody. This analysis indicated lamin A/C as a putative substrate of Akt in C2C12 cells. In vitro phosphorylation of endogenous lamin A/C by recombinant Akt further validated this result. Moreover, by phosphopeptide analysis and point mutation, we established that lamin A/C is phosphorylated by Akt at Ser404, in an evolutionary conserved Akt motif. To delve deeper into this, we raised an antibody against the lamin A Ser404 phosphopeptide which allowed us to determine that phosphorylation of lamin A Ser404 is triggered by the well-known Akt activator insulin, and is therefore to be regarded as a physiological response. Remarkably, expression of S404A lamin A in primary cells from healthy tissue caused the nuclear abnormalities that are a hallmark of Emery-Dreifuss muscular dystrophy (EDMD) cells. Indeed, it is known that mutations at several sites in lamin A/C cause autosomal dominant EDMD. Very importantly, we show here that Akt failed to phosphorylate lamin A/C in primary cells from an EDMD-2 patient with lamin A/C mutated in the Akt consensus motif. Together, our data demonstrate that lamin A/C is a novel signaling target of Akt, and implicate Akt phosphorylation of lamin A/C in the correct function of the nuclear lamina.

• Authors: Vittoria Cenni, Jessika Bertacchini, Francesca Beretti, Giovanna Lattanzi, Alberto Bavelloni, Massimo Riccio, Maria Ruzzene, Oriano Marin, Giorgio Arrigoni, Veena Parnaik, Manfred Wehnert, Nadir M Maraldi, Anto de Pol, Lucio Cocco, Sandra Marmiroli
• Journal: Journal of proteome research (J Proteome Res) Vol. 7 Issue 11 Pg. 4727-35 (Nov 2008) ISSN: 1535-3893 [Print] United States
• PMID: 18808171 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Lamin Type A
• Recombinant Proteins
• Serine
• Proto-Oncogene Proteins c-akt

Topics

• Animals
• Cell Line
• Cell Nucleus (genetics, metabolism)
• Humans
• Kidney (cytology)
• Lamin Type A (genetics, metabolism)
• Mice
• Myoblasts (metabolism)
• Phosphorylation
• Proteomics (methods)
• Proto-Oncogene Proteins c-akt (genetics, metabolism)
• Recombinant Proteins (metabolism)
• Serine (metabolism)
• Transfection