Mapping membrane lipids in the developing and adult mouse retina under physiological and pathological conditions using mass spectrometry

Abstract

Membrane phospholipids play pivotal roles in various cellular processes, and their levels are tightly regulated. In the retina, phospholipids had been scrutinized because of their distinct composition and requirement in visual transduction. However, how lipid composition changes during retinal development remains unclear. Here, we used liquid chromatography–mass spectrometry (LC-MS) to assess the dynamic changes in the levels of two main glycerophospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), in the developing mouse retina under physiological and pathological conditions. The total levels of PC and PE increased during retinal development, and individual lipid species exhibited distinct level changes. The amount of very-long-chain PC and PE increased dramatically in the late stages of retinal development. The mRNA levels of Elovl2 and Elovl4 , genes encoding enzymes essential for the synthesis of very-long-chain polyunsaturated fatty acids, increased in developing photoreceptors. Cell sorting based on CD73 expression followed by LC-MS revealed distinct changes in PC and PE levels in CD73-positive rod photoreceptors and CD73-negative retinal cells. Finally, using the NaIO 3 -induced photoreceptor degeneration model, we identified photoreceptor-specific changes in PC and PE levels from 1 day after NaIO 3 administration, before the outer segment of photoreceptors displayed morphological impairment. In conclusion, our findings provide insight into the dynamic changes in PC and PE levels in the developing and adult mouse retina under physiological and pathological conditions. Furthermore, we provide evidence that cell sorting followed by LC-MS is a promising approach for investigating the relevance of lipid homeostasis in the function of different retinal cell types.

Lysophosphatidylcholine acyltransferase 1 controls mitochondrial reactive oxygen species generation and survival of retinal photoreceptor cells

“…As shown in Figure 3, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed a gradual alteration in retinal PC composition during maturation. Consistent with previous studies (12,13), the proportion of DHA-containing PC species, including PC 38:6, PC 40:6, and PC 44:12, increased along with retinal maturation (Fig. 3).…”

“…Photoreceptor cells possess a unique membrane phospholipid composition (12). In the membrane of photoreceptor cells, especially in the outer segment (OS) discs, docosahexaenoic acid (DHA)-containing phospholipids are extremely enriched.…”

Lysophosphatidylcholine acyltransferase 1 controls the mitochondrial reactive oxygen species generation and survival of the retinal photoreceptor cells

“…As shown in Figure 3, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed a gradual alteration in retinal PC composition during maturation. Consistent with previous studies (11,12), the proportion of DHA-containing PC species, including PC 38:6, PC 40:6, and PC 44:12, increased along with retinal maturation (Figure 3). Coinciding with the onset of photoreceptor cell apoptosis in Lpcat1 KO, DPPC, a major product of LPCAT1, was increased in the retina of WT mice between 1 and 2 weeks of age (Figure 3).…”

“…Photoreceptor cells possess a unique membrane phospholipid composition (11). In the membrane of photoreceptor cells, especially in the outer segment (OS) discs, docosahexaenoic acid (DHA)-containing phospholipids are extremely enriched.…”

Nano-scale resolution of native retinal rod disk membranes reveals differences in lipid composition

“…Cholesterol has also been found to be necessary for rhodopsin activity, although high concentrations reduce its signaling efficiency ( Mitchell et al, 1990 , 1992 ; Palczewski, 2006 ). Indeed, many components of the membrane can have a profound impact on the function of the membrane proteins therein, making high-resolution study of membrane environments critical to the overall characterization of membrane proteins ( Zimmerman and Keys, 1989 ; Bush et al, 1991 ; Gibson and Brown, 1993 ; Suh et al, 1994 ; Albert et al, 1998 ; Agbaga et al, 2008 ; Berdeaux et al, 2010 ; Giusto et al, 2010 ; Bennett et al, 2014 ; Gorusupudi et al, 2021 ; Hamano et al, 2021 ). Early work by Falk and Fatt (1969) on the ultra-structure of ROS membranes showed a remarkable ability of the outer rim region of ROS disks to resist disruption after OsO 4 fixation.…”