Characterization of Leber Congenital Amaurosis-associated NMNAT1 Mutants

J Biol Chem. 2015 Jul 10;290(28):17228-38. doi: 10.1074/jbc.M115.637850. Epub 2015 May 27.


Leber congenital amaurosis 9 (LCA9) is an autosomal recessive retinal degeneration condition caused by mutations in the NAD(+) biosynthetic enzyme NMNAT1. This condition leads to early blindness but no other consistent deficits have been reported in patients with NMNAT1 mutations despite its central role in metabolism and ubiquitous expression. To study how these mutations affect NMNAT1 function and ultimately lead to the retinal degeneration phenotype, we performed detailed analysis of LCA-associated NMNAT1 mutants, including the expression, nuclear localization, enzymatic activity, secondary structure, oligomerization, and promotion of axonal and cellular integrity in response to injury. In many assays, most mutants produced results similar to wild type NMNAT1. Indeed, NAD(+) synthetic activity is unlikely to be a primary mechanism underlying retinal degeneration as most LCA-associated NMNAT1 mutants had normal enzymatic activity. In contrast, the secondary structure of many NMNAT1 mutants was relatively less stable as they lost enzymatic activity after heat shock, whereas wild type NMNAT1 retains significant activity after this stress. These results suggest that LCA-associated NMNAT1 mutants are more vulnerable to stressful conditions that lead to protein unfolding, a potential contributor to the retinal degeneration observed in this syndrome.

Keywords: Leber congenital amaurosis; NMNAT; metabolic disease; neuroprotection; nicotinamide adenine dinucleotide (NAD); retinal degeneration; structural biology.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cells, Cultured
  • Enzyme Stability
  • HEK293 Cells
  • Humans
  • Kinetics
  • Leber Congenital Amaurosis / enzymology*
  • Leber Congenital Amaurosis / etiology
  • Leber Congenital Amaurosis / genetics*
  • Mice
  • Mutant Proteins / chemistry
  • Mutant Proteins / genetics*
  • Mutant Proteins / metabolism*
  • Neurons / enzymology
  • Neurons / pathology
  • Nicotinamide-Nucleotide Adenylyltransferase / chemistry
  • Nicotinamide-Nucleotide Adenylyltransferase / genetics*
  • Nicotinamide-Nucleotide Adenylyltransferase / metabolism*
  • Phenotype
  • Protein Structure, Quaternary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Retinal Degeneration / enzymology
  • Retinal Degeneration / etiology
  • Retinal Degeneration / genetics


  • Mutant Proteins
  • Recombinant Proteins
  • NMNAT1 protein, human
  • Nicotinamide-Nucleotide Adenylyltransferase

Supplementary concepts

  • Amaurosis congenita of Leber, type 9

Associated data

  • PDB/1KQN