Altered protein dynamics of disease-associated lamin A mutants

Howard J Worman,Cecilia Östlund,Susan Gilchrist,Nick Gilbert,Wendy A Bickmore,Paul Perry

doi:10.1186/1471-2121-5-46

Howard J Worman, Cecilia Östlund

Open Access

https://doi.org/10.1186/1471-2121-5-46

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Abstract

BackgroundRecent interest in the function of the nuclear lamina has been provoked by the discovery of lamin A/C mutations in the laminopathy diseases. However, it is not understood why mutations in lamin A give such a range of tissue-specific phenotypes. Part of the problem in rationalising genotype-phenotype correlations in the laminopathies is our lack of understanding of the function of normal and mutant lamin A. To investigate this we have used photobleaching in human cells to analyse the dynamics of wild-type and mutant lamin A protein at the nuclear periphery.ResultsWe have found that a large proportion of wild-type lamin A at the nuclear periphery is immobile, but that there is some slow movement of lamin A within the nuclear lamina. The mobility of an R482W mutant lamin A was indistinguishable from wild-type, but increased mobility of L85R and L530P mutant proteins within the nuclear lamina was found. However, the N195K mutant shows the most enhanced protein mobility, both within the nucleoplasm and within the lamina.ConclusionThe slow kinetics of lamin A movement is compatible with its incorporation into a stable polymer that only exchanges subunits very slowly. All of the myopathy-associated lamin A mutants that we have studied show increased protein movement compared with wild-type. In contrast, the dynamic behaviour of the lipodystrophy-associated lamin A mutant was indistinguishable from wild-type. This supports the hypothesis that the underlying defect in lamin A function is quite distinct in the laminopathies that affect striated muscle, compared to the diseases that affect adipose tissue. Our data are consistent with an alteration in the stability of the lamin A molecules within the higher-order polymer at the nuclear lamina in myopathies.

Highlights

Recent interest in the function of the nuclear lamina has been provoked by the discovery of lamin A/C mutations in the laminopathy diseases
R482W and L530P are associated with different disease phenotypes, and they are both within the globular domain, R482W is a surface residue, whilst L530P is internal (Figure 1B)
The R482W mutation is associated with familial partial lipodystrophy (FPLD), and other lamin A mutations found in this disease are either a loss of positive charge at R482, or K486, or the gain of a negative charge (G465D)

Summary

Introduction

Recent interest in the function of the nuclear lamina has been provoked by the discovery of lamin A/C mutations in the laminopathy diseases. Part of the problem in rationalising genotype-phenotype correlations in the laminopathies is our lack of understanding of the function of normal and mutant lamin A To investigate this we have used photobleaching in human cells to analyse the dynamics of wild-type and mutant lamin A protein at the nuclear periphery. BMC Cell Biology 2004, 5:46 http://www.biomedcentral.com/1471-2121/5/46 ments that resemble those formed in vivo, lamins assemble in vitro into paracrystalline arrays rather than filaments [4]. This suggests that, in vivo, assembly of correct lamin higher-order structures requires the interaction with other molecules/proteins. There is an interaction between lamins A/C and the INM proteins LAP2β [11] and muscle-specific nesprin1 [12]

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