Lipidomics Characterization of Biosynthetic and Remodeling Pathways of Cardiolipins in Genetically and Nutritionally Manipulated Yeast Cells

Cardioipins
(CLs) are unique tetra-acylated phospholipids of mitochondria
and define the bioenergetics and regulatory functions of these organelles.
An unresolved paradox is the high uniformity of CL molecular species
(tetra-linoleoyl-CL) in the heart, liver, and skeletal musclesin
contrast to their high diversification in the brain. Here, we combined
liquid chromatography–mass-spectrometry-based phospholipidomics
with genetic and nutritional manipulations to explore CLs’
biosynthetic vs postsynthetic remodeling processes in S. cerevisiae yeast cells. By applying the differential phospholipidomics analysis,
we evaluated the contribution of Cld1 (CL-specific phospholipase A)
and Taz1 (acyl-transferase) as the major regulatory mechanisms of
the remodeling process. We further established that nutritional “pressure”
by high levels of free fatty acids triggered a massive synthesis of
homoacylated molecular species in all classes of phospholipids, resulting
in the preponderance of the respective homoacylated CLs. We found
that changes in molecular speciation of CLs induced by exogenous C18-fatty
acids (C18:1 and C18:2) in wild-type (wt) cells did not occur in any
of the remodeling mutant cells, including cld1Δ, taz1Δ, and cld1Δtaz1Δ. Interestingly, molecular speciation of CLs in wt and double mutant
cells cld1Δtaz1Δ was markedly different.
Given that the bioenergetics functions are preserved in the double
mutant, this suggests that the accumulated MLCLrather than
the changed CL speciationare the likely major contributors
to the mitochondrial dysfunction in taz1Δ mutant
cells (also characteristic of Barth syndrome). Biochemical studies
of Cld1 specificity and computer modeling confirmed the hydrolytic
selectivity of the enzyme toward C16-CL substrates and the preservation
of C18:1-containing CL species.