MEMBRANE RESTRUCTURING EVENTS DURING THE ENZYMATIC GENERATION OF CERAMIDES WITH VERY LONG-CHAIN POLYUNSATURATED FATTY ACIDS

PEÑALVA, DANIEL ALEJANDRO; ANTOLLINI, SILVIA; AMBROGGIO, ERNESTO; AVELDAÑO, MARTA I.; FANANI, MARIA LAURA

LANGMUIR

AMER CHEMICAL SOC

Año: 2018 vol. 34 p. 4398 - 4407

0743-7463

In rat sperm head, sphingomyelin (SM) species that contain very long chain PUFA (V-SM) become ceramides (V-Cer) after inducing in vitro the acrosomal reaction. The reason for such a specific location of this conversion, catalysed by a sphingomyelinase (SMase), has received little investigation so far. Here, the effects of SMase were compared in unilamellar vesicles (LUVs, GUVs) containing phosphatidylcholine and either V-SM or a palmitate-rich SM (P-SM). In uniformly sized LUVs at 37 oC, more V-Cer was generated, and more rapidly, than P-Cer. Nephelometry and dynamic light scattering showed that LUVs tended to form large lipid particles more intensely, and FRET increases suggested that lateral lipid mixing was more marked when V-Cer rather than P-Cer was produced. As reported by Laurdan and DPH, the production of V-Cer resulted in higher and faster restriction in lipid mobility than that of P-Cer, implying a stronger increase in membrane dehydration and microviscosity. Moreover, DPH anisotropy suggested a higher solubility of V-Cer than of P-Cer in the liquid-disordered phase. At room temperature, liquid-condensed lateral domains appeared in P-SM-, but not in V-SM-containing GUVs. The former maintained their size while losing their contents gradually during SMase action, while the latter became permeable earlier and reduced their size in few minutes until suddenly collapsing. The fast and potent generation of V-Cer may contribute to the membrane restructuring events that occur on the acrosome-reacting sperm head.