Comparative Stability and Clearance of [Met30]Transthyretin and [Met119]Transthyretin

Authors

  • Isabel Longo Alves,

    1. Institute de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
    2. Centro de Estudos de Paramiloidose, Hospital de Santo António, Porto, Portugal
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  • Marguerite T. Hays,

    1. Department of Veterans Affairs, Medical Center, Palo Alto, USA
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  • Maria João Mascarenhas Saraiva

    Corresponding author
    1. Institute de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
    2. Centro de Estudos de Paramiloidose, Hospital de Santo António, Porto, Portugal
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M. J. M. Saraiva, Institute de Ciências Biomédicas de Abel Salazar, Largo Prof. Abel Salazar, 2, P-4050 Porto, Portugal
Fax: +351 2 2001918.

Abstract

[Met119]Transthyretin has been described as a non-amyloidogenic transthyretin variant. In Portugal, it has also been found in compound heterozygotic individual carriers of [Met30]transthyretin, the most prevalent variant associated with familial amyloidotic polyneuropathy. In these individuals, the evolution of the disease seems to be more benign than in typical [Met30]transthyretin carriers, suggesting a protective effect of [Met119]transthyretin on the pathogenic effects of [Met30]transthyretin. To study the mechanisms of this protective effect, we performed comparative in vivo clearance studies. Heterotetrameric [Met119]transthyretin showed a slower clearance, whereas homotetrameric [Met30]transthyretin presented a faster clearance. These data correlate with the relative TTR levels present in carriers of these mutations. Comparative analyses of the resistance to dissociation into monomers of serum transthyretin by 4M urea isoelectric focusing suggested a higher tetrameric stability of transthyretin in [Met119]transthyretin carriers, in contrast to a lower stability in [Met30]transthyretin carriers. The compound heterozygotes presented a pattern similar to the normal individuals. Our results suggest that the protective clinical effect of the Met119 mutation possibly involves the stabilisation of the tetrameric structure of transthyretin. Whether this behaviour correlates with the different metabolism found for the two variants is not known. The approaches reported here open some possibilities for the study and development of future therapeutic agents of familial amyloidotic polyneuropathy.

Abbreviations
TTR

transthyretin

FAP

familial amyloidotic polyneuropathy

FAC

familial amyloidotic cardiomyopathy

RID

radial immunodiffusion

RBP

retinol-binding protein

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