Deleterious assembly of the lamin A/C mutant p.S143P causes ER stress in familial dilated cardiomyopathy

: West G, Gullmets J, Virtanen L, Li SP, Keinanen A, Shimi T, Mauermann M, Helio T, Kaartinen M, Ollila L, Kuusisto J, Eriksson JE, Goldman RD, Herrmann H, Taimen P

Publisher: COMPANY OF BIOLOGISTS LTD

: 2016

: Journal of Cell Science

: JOURNAL OF CELL SCIENCE

: J CELL SCI

: 129

: 14

: 2732

: 2743

: 12

: 0021-9533

: 1477-9137

DOI: https://doi.org/10.1242/jcs.184150(external)

Mutation of the LMNA gene, encoding nuclear lamin A and lamin C (hereafter lamin A/C), is a common cause of familial dilated cardiomyopathy (DCM). Among Finnish DCM patients, the founder mutation c.427T>C (p.S143P) is the most frequently reported genetic variant. Here, we show that p.S143P lamin A/C is more nucleoplasmic and soluble than wild-type lamin A/C and accumulates into large intranuclear aggregates in a fraction of cultured patient fibroblasts as well as in cells ectopically expressing either FLAG- or GFP-tagged p.S143P lamin A. In fluorescence loss in photobleaching (FLIP) experiments, non-aggregated EGFP-tagged p.S143P lamin A was significantly more dynamic. In in vitro association studies, p.S143P lamin A failed to form appropriate filament structures but instead assembled into disorganized aggregates similar to those observed in patient cell nuclei. A whole-genome expression analysis revealed an elevated unfolded protein response (UPR) in cells expressing p.S143P lamin A/C. Additional endoplasmic reticulum (ER) stress induced by tunicamycin reduced the viability of cells expressing mutant lamin further. In summary, p.S143P lamin A/C affects normal lamina structure and influences the cellular stress response, homeostasis and viability.