Sterol efflux from mammalian cells induced by human serum albumin-phospholipid complexes. Dependence on phospholipid acyl chain length, degree of saturation, and net charge.

The synthesis of fatty acids de novo from acetate and the elongation of exogenous satuated fatty acids (C12-C18) by the psychrophilic bacterium Micrococcus cryophilus (A.T.C.C. 15174) grown at 1 or 20 degrees C was investigated. M. cryophilus normally contains only C16 and C18 acyl chains in its phospholipids, and the C18/C16 ratio is altered by changes in growth temperature. The bacterium was shown to regulate strictly its phospholipid acyl chain length and to be capable of directly elongating myristate and palmitate, and possibly laurate, to a mixture of C16 and C18 acyl chains. Retroconversion of stearate into palmitate also occurred. Fatty acid elongation could be distinguished from fatty acid synthesis de novo by the greater sensitivity of fatty acid elongation to inhibition by NaAsO2 under conditions when the supply of ATP and reduced nicotinamide nucleotides was not limiting. It is suggested that phospholipid acyl chain length may be controlled by a membrane-bound elongase enzyme, which interconverts C16 and C18 fatty acids via a C14 intermediate; the activity of the enzyme could be regulated by membrane lipid fluidity.

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Chain Length-dependent Binding of Fatty Acid Anions to Human Serum Albumin Studied by Site-directed Mutagenesis

Journal of Molecular Biology ◽

10.1016/j.jmb.2006.08.056 ◽

2006 ◽

Vol 363 (3) ◽

pp. 702-712 ◽

Cited By ~ 63

Author(s):

Ulrich Kragh-Hansen ◽

Hiroshi Watanabe ◽

Keisuke Nakajou ◽

Yasunori Iwao ◽

Masaki Otagiri

Keyword(s):

Fatty Acid ◽

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Chain Length ◽

Site Directed Mutagenesis ◽

Directed Mutagenesis

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Altered chain-length and glycosylation modify the pharmacokinetics of human serum albumin

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics ◽

10.1016/j.bbapap.2008.11.022 ◽

2009 ◽

Vol 1794 (4) ◽

pp. 634-641 ◽

Cited By ~ 13

Author(s):

Yasunori Iwao ◽

Mikako Hiraike ◽

Ulrich Kragh-Hansen ◽

Keiichi Kawai ◽

Ayaka Suenaga ◽

...

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Chain Length

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Changes of net charge and α-helical content affect the pharmacokinetic properties of human serum albumin

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics ◽

10.1016/j.bbapap.2007.09.001 ◽

2007 ◽

Vol 1774 (12) ◽

pp. 1582-1590 ◽

Cited By ~ 17

Author(s):

Yasunori Iwao ◽

Mikako Hiraike ◽

Ulrich Kragh-Hansen ◽

Katsumi Mera ◽

Taishi Noguchi ◽

...

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Net Charge ◽

Helical Content ◽

Pharmacokinetic Properties

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Phospholipid exchange shows insulin receptor activity is supported by both the propensity to form wide bilayers and ordered domains (rafts)

10.1101/2021.04.27.440802 ◽

2021 ◽

Author(s):

Pavana Suresh ◽

W. Todd Miller ◽

Erwin London

Keyword(s):

Insulin Receptor ◽

Chain Length ◽

Mammalian Cells ◽

Plasma Membranes ◽

Acyl Chain ◽

Phospholipid Composition ◽

Domain Formation ◽

Lipid Structure ◽

Acyl Chain Length ◽

Lipid Exchange

ABSTRACTUsing efficient methyl-alpha-cyclodextrin mediated lipid exchange, we studied the effect of altering plasma membrane outer leaflet phospholipid composition upon the activity of insulin receptor (IR) in mammalian cells. After substitution of endogenous lipids with lipids having an ability to form liquid ordered (Lo) domains (sphingomyelins) or liquid disordered (Ld) domains (unsaturated phosphatidylcholines (PCs)), we found that the propensity of lipids to form ordered domains is required for high IR activity. Additional substitution experiments using a series of saturated PCs showed that IR activity increased substantially with increasing acyl chain length. Increasing acyl chain length increases both bilayer width and the propensity to form ordered domains. To distinguish the effects of membrane width and domain formation, we incorporated purified IR into alkyl maltoside micelles with increasing hydrocarbon lengths. IR activity increases with increased chain length, but more modestly than by increasing lipid acyl chain length in cells. This suggests that the ability to form Lo domains as well as wide bilayer width contributes to increased IR activity. Inhibition of phosphatases with sodium orthovanadate showed that some of the lipid dependence of IR activity upon lipid structure reflected protection from phosphatases by lipids that support Lo domain formation. The results are consistent with a model in which a combination of bilayer width and ordered domain formation modulate IR activity via effects upon IR conformation and accessibility to phosphatases.SignificanceThis study shows how methyl-α-cyclodextrin mediated lipid exchange can be used to probe the influence of lipid structure upon the functioning of a transmembrane receptor. Plasma membranes having a propensity to form Lo domains are required to support a high level of IR activity. The studies indicate this may reflect an effect of lipid environment upon IR domain localization, which in turn alters its conformation and vulnerability to phosphatases. Alterations in lipid composition could conceivably regulate IR activity in vivo.

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Structural basis of transport of lysophospholipids by human serum albumin

Biochemical Journal ◽

10.1042/bj20090913 ◽

2009 ◽

Vol 423 (1) ◽

pp. 23-30 ◽

Cited By ~ 30

Author(s):

Shihui Guo ◽

Xiaoli Shi ◽

Feng Yang ◽

Liqing Chen ◽

Edward J. Meehan ◽

...

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Extracellular Space ◽

Intracellular Transport ◽

Acyl Chain ◽

Structural Basis ◽

Fluorescence Measurement ◽

Polar Head Group ◽

Fatty Acid Binding

Lysophospholipids play important roles in cellular signal transduction and are implicated in many biological processes, including tumorigenesis, angiogenesis, immunity, atherosclerosis, arteriosclerosis, cancer and neuronal survival. The intracellular transport of lysophospholipids is through FA (fatty acid)-binding protein. Lysophospholipids are also found in the extracellular space. However, the transport mechanism of lysophospholipids in the extracellular space is unknown. HSA (human serum albumin) is the most abundant carrier protein in blood plasma and plays an important role in determining the absorption, distribution, metabolism and excretion of drugs. In the present study, LPE (lysophosphatidylethanolamine) was used as the ligand to analyse the interaction of lysophospholipids with HSA by fluorescence quenching and crystallography. Fluorescence measurement showed that LPE binds to HSA with a Kd (dissociation constant) of 5.6 μM. The presence of FA (myristate) decreases this binding affinity (Kd of 12.9 μM). Moreover, we determined the crystal structure of HSA in complex with both myristate and LPE and showed that LPE binds at Sudlow site I located in subdomain IIA. LPE occupies two of the three subsites in Sudlow site I, with the LPE acyl chain occupying the hydrophobic bottom of Sudlow site I and the polar head group located at Sudlow site I entrance region pointing to the solvent. This orientation of LPE in HSA suggests that HSA is capable of accommodating other lysophospholipids and phospholipids. The study provides structural information on HSA–lysophospholipid interaction and may facilitate our understanding of the transport and distribution of lysophospholipids.

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Different rates of flux through the biosynthetic pathway for long-chain versus very-long-chain sphingolipids

The Journal of Lipid Research ◽

10.1194/jlr.ra120000984 ◽

2020 ◽

Vol 61 (10) ◽

pp. 1341-1346

Author(s):

Iris D. Zelnik ◽

Giora Volpert ◽

Leena E. Viiri ◽

Dimple Kauhanen ◽

Tamar Arazi ◽

...

Keyword(s):

Fatty Acids ◽

Chain Length ◽

Biosynthetic Pathway ◽

Acyl Chain ◽

Degree Of Saturation ◽

Disease States ◽

Acyl Chain Length ◽

Long Chain Base ◽

Acyl Chains ◽

Long Chain

The backbone of all sphingolipids (SLs) is a sphingoid long-chain base (LCB) to which a fatty acid is N-acylated. Considerable variability exists in the chain length and degree of saturation of both of these hydrophobic chains, and recent work has implicated ceramides with different LCBs and N-acyl chains in distinct biological processes; moreover, they may play different roles in disease states and possibly even act as prognostic markers. We now demonstrate that the half-life, or turnover rate, of ceramides containing diverse N-acyl chains is different. By means of a pulse-labeling protocol using stable-isotope, deuterated free fatty acids, and following their incorporation into ceramide and downstream SLs, we show that very-long-chain (VLC) ceramides containing C24:0 or C24:1 fatty acids turn over much more rapidly than long-chain (LC) ceramides containing C16:0 or C18:0 fatty acids due to the more rapid metabolism of the former into VLC sphingomyelin and VLC hexosylceramide. In contrast, d16:1 and d18:1 ceramides show similar rates of turnover, indicating that the length of the sphingoid LCB does not influence the flux of ceramides through the biosynthetic pathway. Together, these data demonstrate that the N-acyl chain length of SLs may not only affect membrane biophysical properties but also influence the rate of metabolism of SLs so as to regulate their levels and perhaps their biological functions.

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