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

TY - JOUR

T1 - Protein misfolding is the molecular mechanism underlying MCADD identified in newborn screening

AU - Maier, Esther M

AU - Gersting, Søren W

AU - Kemter, Kristina F

AU - Jank, Johanna M

AU - Reindl, Maria

AU - Messing, Dunja D

AU - Truger, Marietta S

AU - Sommerhoff, Christian P

AU - Muntau, Ania C

PY - 2009/5/1

Y1 - 2009/5/1

N2 - 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.

AB - 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.

KW - Acyl-CoA Dehydrogenase

KW - Amino Acid Substitution

KW - Enzyme Stability

KW - Female

KW - Humans

KW - Infant, Newborn

KW - Kinetics

KW - Lipid Metabolism, Inborn Errors

KW - Male

KW - Molecular Conformation

KW - Molecular Sequence Data

KW - Mutation, Missense

KW - Neonatal Screening

KW - Protein Folding

U2 - 10.1093/hmg/ddp079

DO - 10.1093/hmg/ddp079

M3 - SCORING: Journal article

C2 - 19224950

VL - 18

SP - 1612

EP - 1623

JO - HUM MOL GENET

JF - HUM MOL GENET

SN - 0964-6906

IS - 9

ER -