Comprehensive survey of disease-causing missense mutations of the cholesterol synthesis enzyme NSDHL: Low temperature and a chemical chaperone rescue low protein expression of select mutants

Cholesterol is essential to human life. Perturbations to any of the 22 cholesterol synthesis enzymes can lead to devastating developmental diseases. Each enzyme is exquisitely regulated both transcriptionally and post-translationally, playing a critical role in providing cholesterol to cells. We examined 13 missense mutations and one deletion mutation in the cholesterol synthesis enzyme NSDHL (NAD(P) Dependent Steroid Dehydrogenase-Like), known to cause the X-linked developmental disorders CHILD (congenital hemidysplasia with ichthyosiform erythroderma and limb defects) syndrome and CK syndrome. Little is known about the effect of these missense mutations on the stability and function of NSDHL. Here we show that protein expression levels were low for all mutants, but some could be rescued by a lower temperature (30°C vs. 37°C) and/or the chemical chaperone glycerol. Additionally, heat shock proteins 70 and 90 are needed for optimal NSDHL protein expression suggesting that disease mutations in NSDHL may interfere with this interaction, perhaps during translation resulting in lower protein synthesis. Our findings that these disease-causing mutations reduce NSDHL protein expression, but some respond to lower temperature and/or the chemical chaperone glycerol, can help inform future treatments for CHILD and CK syndrome.