TY - JOUR
T1 - Loss of mitochondrial DNA-encoded protein ND1 results in disruption of complex I biogenesis during early stages of assembly
AU - Lim, Chern
AU - Hroudová, Jana
AU - Van Bergen, Nicole J.
AU - Lopez Sanchez, M. Isabel G
AU - Trounce, Ian A.
AU - McKenzie, Matthew
PY - 2016/6/1
Y1 - 2016/6/1
N2 - Mitochondrial complex I (NADH:ubiquinone oxidoreductase) must be assembled precisely from 45 protein subunits for it to function correctly. One of its mitochondrial DNA (mtDNA) encoded subunits, ND1, is incorporated during the early stages of complex I assembly. However, little is known about how mutations in ND1 affect this assembly process. We found that in human 143B cybrid cells carrying a homoplasmic MT-ND1 mutation, ND1 protein could not be translated. As a result, the early stages of complex I assembly were disrupted, with mature complex I undetectable and complex I-linked respiration severely reduced to 2.0% of control levels. Interestingly, complex IV (ferrocytochrome c:oxygen oxidoreductase) steady-state levels were also reduced to 40.3%, possibly due to its diminished stability in the absence of respiratory supercomplex formation. This was in comparison with 143B cybrid controls (that contained wild-type mtDNA on the same nuclear background), which exhibited normal complex I, complex IV, and supercomplex assembly. We conclude that the loss of ND1 stalls complex I assembly during the early stages of its biogenesis, which not only results in the loss of mature complex I but also disrupts the stability of complex IV and the respiratory supercomplex to cause mitochondrial dysfunction.
AB - Mitochondrial complex I (NADH:ubiquinone oxidoreductase) must be assembled precisely from 45 protein subunits for it to function correctly. One of its mitochondrial DNA (mtDNA) encoded subunits, ND1, is incorporated during the early stages of complex I assembly. However, little is known about how mutations in ND1 affect this assembly process. We found that in human 143B cybrid cells carrying a homoplasmic MT-ND1 mutation, ND1 protein could not be translated. As a result, the early stages of complex I assembly were disrupted, with mature complex I undetectable and complex I-linked respiration severely reduced to 2.0% of control levels. Interestingly, complex IV (ferrocytochrome c:oxygen oxidoreductase) steady-state levels were also reduced to 40.3%, possibly due to its diminished stability in the absence of respiratory supercomplex formation. This was in comparison with 143B cybrid controls (that contained wild-type mtDNA on the same nuclear background), which exhibited normal complex I, complex IV, and supercomplex assembly. We conclude that the loss of ND1 stalls complex I assembly during the early stages of its biogenesis, which not only results in the loss of mature complex I but also disrupts the stability of complex IV and the respiratory supercomplex to cause mitochondrial dysfunction.
KW - Blue native PAGE
KW - Oxidative phosphorylation
KW - Respiratory chain
KW - Supercomplex
UR - http://www.scopus.com/inward/record.url?scp=84973165770&partnerID=8YFLogxK
U2 - 10.1096/fj.201500137R
DO - 10.1096/fj.201500137R
M3 - Article
AN - SCOPUS:84973165770
VL - 30
SP - 2236
EP - 2248
JO - The FASEB Journal
JF - The FASEB Journal
SN - 0892-6638
IS - 6
ER -