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Protein misfolding is the molecular mechanism underlying MCADD identified in newborn screening.

Abstract：

:Newborn screening (NBS) for medium-chain acyl-CoA dehydrogenase deficiency (MCADD) revealed a higher birth prevalence and genotypic variability than previously estimated, including numerous novel missense mutations in the ACADM gene. On average, these mutations are associated with milder biochemical phenotypes raising the question about their pathogenic relevance. In this study, we analyzed the impact of 10 ACADM mutations identified in NBS (A27V, Y42H, Y133H, R181C, R223G, D241G, K304E, R309K, I331T and R388S) on conformation, stability and enzyme kinetics of the corresponding proteins. Partial to total rescue of aggregation by co-overexpression of GroESL indicated protein misfolding. This was confirmed by accelerated thermal unfolding in all variants, as well as decreased proteolytic stability and accelerated thermal inactivation in most variants. Catalytic function varied from high residual activity to markedly decreased activity or substrate affinity. Mutations mapping to the beta-domain of the protein predisposed to severe destabilization. In silico structural analyses of the affected amino acid residues revealed involvement in functionally relevant networks. Taken together, our results substantiate the hypothesis of protein misfolding with loss-of-function being the common molecular basis in MCADD. Moreover, considerable structural alterations in all analyzed variants do not support the view that novel mutations found in NBS bear a lower risk of metabolic decompensation than that associated with mutations detected in clinically ascertained patients. Finally, the detailed insight into how ACADM missense mutations induce loss of MCAD function may provide guidance for risk assessment and counseling of patients, and in future may assist delineation of novel pharmacological strategies.

journal_name

Hum Mol Genet

journal_title

Human molecular genetics

authors

Maier EM,Gersting SW,Kemter KF,Jank JM,Reindl M,Messing DD,Truger MS,Sommerhoff CP,Muntau AC

doi

10.1093/hmg/ddp079

subject

Has Abstract

pub_date

2009-05-01 00:00:00

pages

1612-23

issue

eissn

0964-6906

issn

1460-2083

pii

ddp079

journal_volume

pub_type

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Protein misfolding is the molecular mechanism underlying MCADD identified in newborn screening.