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From the body

LPILysophosphatidylinositol

An endogenous lysophospholipid, the reference agonist of the GPR55 receptor; no established activity at CB1 or CB2.

Endogenous
Level of detail

C₂₅H₄₉O₁₂P

CAS 796963-91-2

Family
Endocannabinoid or related mediatorEndocannabinoidome
Molar mass
572.60 g/mol

Updated on

In plain terms

LPI is a fragment of membrane fat that the body's cells make by cutting up a phospholipid; it serves as a signal between cells. It binds a receptor called GPR55, long presented as a cousin of the cannabis receptors, but it is not a cannabinoid and nothing establishes that it acts on CB1 or CB2 receptors. It is not found in hemp and everything known about it comes from the laboratory.

Receptors and activity

Target network

GPR55AgonistEC50 = 35.5 nM · humanG protein dissociation (BRET²), Gα13, human GPR55, 1-palmitoyl-LPI (16:0)
  • Activates
  • Binds or modulates

The lower the cited value, the closer the target sits to LPI: one ring per factor of 100. A target with no measured value stays on the edge.

Where these targets live

Where each target has been found in humans, according to the cited studies. The map shows the target, not an effect of LPI.

Brain, side view
Body, front view
Blood

GPR55GPR55 found in 4 regions of the body

  1. Basal gangliapresentmRNA found in the caudate nucleus and putamen1
  2. BonepresentOsteoclasts and osteoblasts2
  3. Adipose tissuepresentExpressed in visceral adipose tissue3
  4. LiverpresentExpressed in the liver3

Map sources

  1. Sawzdargo M et al. Identification and cloning of three novel human G protein-coupled receptor genes GPR52, PsiGPR53 and GPR55: GPR55 is extensively expressed in human brain. Brain Res Mol Brain Res, 1999 (new tab)
  2. Whyte LS et al. The putative cannabinoid receptor GPR55 affects osteoclast function in vitro and bone mass in vivo. Proc Natl Acad Sci U S A, 2009 (new tab)
  3. Moreno-Navarrete JM et al. The L-α-lysophosphatidylinositol/GPR55 system and its potential role in human obesity. Diabetes, 2012 (new tab)

Cited values

  1. GPR55AgonistEC50 = 35.5 nM · human57 out of 100

    Claff et al. 2025, Nat Commun (new tab) · G protein dissociation (BRET²), Gα13, human GPR55, 1-palmitoyl-LPI (16:0)

  2. TRPV2Modulatorno measured value cited

    In enteroendocrine L cells, blockade or knockdown of TRPV2 abolishes the calcium rise and GLP-1 secretion induced by LPI, which GPR55 agonists do not fully reproduce; LPI accelerates TRPV2 translocation to the membrane (Harada 2017). No direct binding measured.

  3. CB2Modulatorno measured value cited

    In murine mast cells, the accumulation of VEGF, TNF, IL-1α and IL-1β mRNAs induced by LPI is as sensitive to the CB2 antagonist AM630 as to the GPR55 antagonist ML193; no direct binding to CB2 has been demonstrated (Martínez-Aguilar 2023)

Bar length follows the measured value (Ki, Kd, EC50 or IC50), on one scale shared by every entry, from 100 µM to 0.1 nM. A target with no cited value has no bar.

Pharmacology

LPI holds a singular place in the endocannabinoid system literature: it is the reference endogenous agonist of GPR55, a receptor long presented as a third cannabinoid receptor, while the molecule itself is a lysophospholipid and no data establish activity at CB1 or CB2. The identification dates from 2007, when Oka and colleagues showed that LPI, alone among the lysolipids tested, triggers ERK phosphorylation, calcium transients and GTPγS binding in cells expressing GPR55, where cannabinoid ligands fail to do so (Oka 2007); the 2-arachidonoyl species is the most active and the most likely natural ligand, rat brain containing 37.5 nmol/g of LPI across all species (Oka 2009). The structure of the complex, obtained by cryo-electron microscopy in 2025 with the 16:0 species, details the anchoring of the phosphate to arginine 253, the bonds of the inositol head to asparagine 16 and histidine 170, and the exit of the palmitoyl chain towards the membrane between helices IV and V, with an EC50 of 35.5 nM at Gα13 (Claff 2025). Not everything is attributable to GPR55: in enteroendocrine L cells, LPI-induced GLP-1 secretion also depends on the TRPV2 channel and is not reproduced by selective agonists of the receptor (Harada 2017). The cannabinoid pharmacology of GPR55 is contradictory, CB1 antagonists behaving both as agonists and as inhibitors, while Δ9-THCV, CBDV and cannabigerovarin potently inhibit LPI-triggered signalling (Anavi-Goffer 2012). Human data are lacking: no controlled administration, only measurements of endogenous concentrations and an association with obesity (Moreno-Navarrete 2012). No therapeutic benefit is established.

Key sources.

History

Source
An endogenous molecule, absent from cannabis: LPI is a lysophospholipid released by partial hydrolysis of membrane phosphatidylinositols. Rat brain contains 37.5 nmol/g tissue, the dominant acyl chain being stearic acid (50.5 %) ahead of arachidonic acid (22.1 %) (Oka 2009). Its levels rise in ras-transformed cells, which release it into the medium (Falasca 1994; Falasca 1998), and plasma LPI was found higher in obese female patients, correlated with weight and percentage body fat (Moreno-Navarrete 2012). This entry describes the 16:0 species, the one whose structure was solved on GPR55 (Claff 2025).

Biosynthetic pathway

In vivo

LPI arises from partial hydrolysis of membrane phosphatidylinositols rather than from a dedicated synthetic pathway. A phospholipase A2 removes the acyl chain at position 2 and leaves a 1-acyl-LPI, the form of the 16:0 species described here, which keeps its palmitate. DDHD1, first identified as a phosphatidic acid-preferring phospholipase A1, is one of the enzymes producing 2-arachidonoyl-LPI from 1-stearoyl-2-arachidonoyl phosphatidylinositol (Yamashita 2013).

Classification

Family, origin and source verification

Family

Endocannabinoid or related mediator › Endocannabinoidome

Verification

Every fact on this entry was checked against its primary sources on 20 October 2026.

Wikipedia (English)

Lysophosphatidylinositol (new tab)

Article paired by the molecule's structure (InChIKey), revision read on 19 October 2026. Read as a second opinion, never cited as a source.

References

  1. Oka et al. 2007, Biochem Biophys Res Commun: identification of GPR55 as the LPI receptor (new tab)PMID 17765871
  2. Oka et al. 2009, J Biochem: 2-arachidonoyl-LPI, the probable natural ligand of GPR55; content of rat brain (new tab)PMID 18845565
  3. Claff et al. 2025, Nat Commun: structure of the GPR55-G13 complex with 1-palmitoyl-LPI, EC50 35.5 nM (new tab)PMID 40000629
  4. Yamashita et al. 2013, Prostaglandins Other Lipid Mediat: actions and metabolism of LPI, DDHD1, cannabinoid status of GPR55 to be reconsidered (new tab)PMID 23714700
  5. Metz 1986, Biochem Biophys Res Commun: LPI, and not lysophosphatidic acid, stimulates insulin release (new tab)PMID 3527169
  6. Falasca & Corda 1994, Eur J Biochem: elevated levels and mitogenic activity of LPI in k-ras-transformed cells (new tab)PMID 8168525
  7. Falasca et al. 1998, Oncogene: release of LPI by H-Ras-transformed fibroblasts (new tab)PMID 9620553
  8. Ryberg et al. 2007, Br J Pharmacol: GPR55, coupling to Gα13, RhoA, cdc42, rac1; activity of cannabidiol and abnormal-CBD (new tab)PMID 17876302
  9. Anavi-Goffer et al. 2012, J Biol Chem: modulation of LPI/GPR55 signalling by cannabinoids (THCV, CBDV, cannabigerovarin as inhibitors) (new tab)PMID 22027819
  10. Harada et al. 2017, J Biol Chem: LPI triggers GLP-1 secretion via TRPV2 in L cells (new tab)PMID 28533434
  11. Martínez-Aguilar et al. 2023, Int J Mol Sci: mast cell chemotaxis and cytokines, differential involvement of GPR55 and CB2 (new tab)PMID 37047288
  12. Moreno-Navarrete et al. 2012, Diabetes: plasma LPI and GPR55 expression in human obesity (new tab)PMID 22179809
  13. Arifin & Falasca 2016, Metabolites: LPI signalling and metabolic diseases (review) (new tab)DOI 10.3390/metabo6010006
  14. PubChem CID 71296207, 1-hexadecanoyl-sn-glycero-3-phospho-(1'-myo-inositol) (new tab)

Identifiers

Names

Common name
Lysophosphatidylinositol
IUPAC name
[(2R)-2-hydroxy-3-[hydroxy-[(2R,3R,5S,6R)-2,3,4,5,6-pentahydroxycyclohexyl]oxyphosphoryl]oxypropyl] hexadecanoate
Other names
LysoPI · L-alpha-lysophosphatidylinositol · lyso-PI · LPI 16:0 · 1-palmitoyl-sn-glycero-3-phosphoinositol · lysophosphatidylinositol 16:0

Identifiers

Formula
C₂₅H₄₉O₁₂P
CAS
796963-91-2
PubChem CID
71296207(new tab)
InChIKey
UOXRPRZMAROFPH-IESLQMLBSA-N
SMILES
CCCCCCCCCCCCCCCC(=O)OC[C@H](COP(=O)(O)OC1[C@@H]([C@H](C([C@H]([C@H]1O)O)O)O)O)O

Machine-readable entry (JSON)

LLM ingestion format: a structured superset of the entry (identifiers, binding, versioned legal status). Full corpus.