Lipocalin-type
prostaglandin (PG) D2 synthase (L-PGDS) catalyzes the isomerization of
PGH2, a common precursor of the two series of PGs, to produce
PGD2.
PGD2 stimulates three distinct types of
G protein-coupled receptors: (1) D type of
prostanoid (DP) receptors involved in the regulation of sleep,
pain, food intake, and others; (2)
chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2) receptors, in myelination of peripheral nervous system, adipocyte differentiation, inhibition of hair follicle neogenesis, and others; and (3) F type of
prostanoid (FP) receptors, in
dexamethasone-induced cardioprotection. L-PGDS is the same
protein as β-trace, a major
protein in human cerebrospinal fluid (CSF). L-PGDS exists in the central nervous system and male genital organs of various mammals, and human heart; and is secreted into the CSF, seminal plasma, and plasma, respectively. L-PGDS binds retinoic
acids and
retinal with high affinities (Kd < 100 nM) and diverse small lipophilic substances, such as thyroids,
gangliosides,
bilirubin and
biliverdin,
heme,
NAD(P)H, and
PGD2, acting as an extracellular carrier of these substances. L-PGDS also binds
amyloid β
peptides, prevents their fibril formation, and disaggregates
amyloid β fibrils, acting as a major
amyloid β chaperone in human CSF. Here, I summarize the recent progress of the research on
PGD2 and L-PGDS, in terms of its "molecular properties," "cell culture studies," "animal experiments," and "clinical studies," all of which should help to understand the pathophysiological role of L-PGDS and inspire the future research of this multifunctional
lipocalin.