title: Calcium causes a conformational change in lamin A tail domain that promotes farnesyl-mediated membrane association.
abstract: Lamin proteins contribute to nuclear structure and function, primarily at the inner nuclear membrane. The posttranslational processing pathway of lamin A includes farnesylation of the C-terminus, likely to increase membrane association, and subsequent proteolytic cleavage of the C-terminus. Hutchinson Gilford progeria syndrome is a premature aging disorder wherein a mutant version of lamin A, Δ50 lamin A, retains its farnesylation. We report here that membrane association of farnesylated Δ50 lamin A tail domains requires calcium. Experimental evidence and molecular dynamics simulations collectively suggest that the farnesyl group is sequestered within a hydrophobic region in the tail domain in the absence of calcium. Calcium binds to the tail domain with an affinity KD ≈ 250 μM where it alters the structure of the Ig-fold and increases the solvent accessibility of the C-terminus. In 2 mM CaCl2, the affinity of the farnesylated protein to a synthetic membrane is KD ≈ 2 μM, as measured with surface plasmon resonance, but showed a combination of aggregation and binding. Membrane binding in the absence of calcium could not be detected. We suggest that a conformational change induced in Δ50 lamin A with divalent cations plays a regulatory role in the posttranslational processing of lamin A, which may be important in disease pathogenesis.
authors.affiliation: Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Kalinowski
authors.forename: Zhao
authors.initials: Z
authors.lastname: Qin
authors.forename: Kelli
authors.initials: K
authors.lastname: Coffey
authors.forename: Ravi
authors.initials: R
authors.lastname: Kodali
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Buehler
authors.forename: Mathias
authors.initials: M
authors.lastname: Lösche
authors.forename: Kris Noel
authors.initials: KN
authors.lastname: Dahl
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D034904:Lamin Type A / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D017368:Protein Prenylation; D017434:Protein Structure, Tertiary
chemical_list: D034904:Lamin Type A; D008051:Lipid Bilayers; D002118:Calcium