Lamin A Ser404 Is a Nuclear Target of Akt Phosphorylation in C2C12 Cells

Department of Anatomy and Histology and CIPro Proteomics Centre, University of Modena and Reggio Emilia, Via Del Pozzo 71, I-41100 Modena, Italy.
Journal of Proteome Research (Impact Factor: 5). 10/2008; 7(11):4727-35. DOI: 10.1021/pr800262g
Source: PubMed

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.

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Available from: Alberto Bavelloni, Aug 15, 2015
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    • "Phosphorylation of lamins at S404 is specifically triggered by Akt in the PI3-kinase insulin pathway and it has been implicated in proper nuclear lamina organization [Cenni et al., 2008]. Interestingly , the EDMD2 LMNA R401C mutation, within the Akt consensus site of lamin A, reduces protein phosphorylation [Cenni et al., 2008]. "
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    • "Lamin B is also phosphorylated by protein kinase C (PKC)α at S395 and S405 sites, which causes degradation and DNA fragmentation in apoptotic HL60 cells (Hocevar et al., 1993; Shimizu et al., 1998). A recent study showed that lamin A is phosphorylated at S404 by Akt in C2C12 cells, which is presumably a physiological response to insulin (Cenni et al., 2008). There is only one report to date showing lamin cleavage and dissolution of the microtubule network preceding chromatin fragmentation in glutamate-induced cerebellar granule cell apoptosis (Ankarcrona et al., 1996). "
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    ABSTRACT: Lamin A/C is a nuclear lamina constituent mutated in a number of human inherited disorders collectively referred to as laminopathies. The occurrence and significance of lamin A/C interplay with signaling molecules is an old question, suggested by pioneer studies performed in vitro. However, this relevant question has remained substantially unanswered, until data obtained in cellular and organismal models of laminopathies have indicated two main aspects of lamin A function. The first aspect is that lamins establish functional interactions with different protein platforms, the second aspect is that lamin A/C activity and altered function may elicit different effects in different cells and tissue types and even in different districts of the same tissue. Both these observations strongly suggest that signaling mechanisms targeting lamin A/C or its binding partners may regulate such a plastic behavior. A number of very recent data show involvement of kinases, as Akt and Erk, or phosphatases, as PP1 and PP2, in lamin A-linked cellular mechanisms. Moreover, altered activation of signaling in laminopathies and rescue of the pathological phenotype in animal models by inhibitors of signaling pathways, strongly suggest that signaling effectors related to lamin A/C may be implicated in the pathogenesis of laminopathies and may represent targets of therapeutic intervention. In face of such an open perspective of basic and applied research, we review current evidence of lamin A/C interplay with signaling molecules, with particular emphasis on the lamin A-Akt interaction and on the biological significance of their relationship.
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