Lysophosphatidic acid binding proteins

Figure 3. Receptor signalling by sphingosine 1-phosphate (SIP) and lysophosphatidic acid (LPA). G7 Gq/Gi2/i3, guanine nucleotide binding proteins. LPA, lysophosphatidic acid receptors. SIP, sphingosine 1-phosphate receptors.

As shown in Table IVA, the cells bind approximately 5% of the total radioactivity added 32% of this eictivity is associated with the cellular lipid fraction and 64% with the nonlipid (presumably protein) fraction. Of the lipid-associated activity, the distribution of I into cellular phospholipids, lysophosphatides, triacylglycerides, and free fatty acids is shown in Table IVB. The iodination reaction labels a variety of lipids of all classes without preference to charge, acid-base properties, or number of fatty acyl constituents, appears not to label intracellular lipids (e.g., cardiolipin, a major mitochondrial component), and labels lipids on both the exterior and interior hydrophilic surfaces of the plasma membrane (i.e., phosphatidylcholine and sphingomyelin as well as phosphatidyleth-anolamine and phosphatidylserine) (Table IVB). ... 

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