Abstract
Lipid droplets, also called lipid bodies (LB) in inflammatory cells, are important cytoplasmic organelles. However, little is known about the molecular characteristics and functions of LBs in human mast cells (MC). Here, we have analyzed the genesis and components of LBs during differentiation of human peripheral blood-derived CD34(+) progenitors into connective tissue-type MCs. In our serum-free culture system, the maturing MCs, derived from 18 different donors, invariably developed triacylglycerol (TG)-rich LBs. Not known heretofore, the MCs transcribe the genes for perilipins (PLIN)1-4, but not PLIN5, and PLIN2 and PLIN3 display different degrees of LB association. Upon MC activation and ensuing degranulation, the LBs were not cosecreted with the cytoplasmic secretory granules. Exogenous arachidonic acid (AA) enhanced LB genesis in Triacsin C-sensitive fashion, and it was found to be preferentially incorporated into the TGs of LBs. The large TG-associated pool of AA in LBs likely is a major precursor for eicosanoid production by MCs. In summary, we demonstrate that cultured human MCs derived from CD34(+) progenitors in peripheral blood provide a new tool to study regulatory mechanisms involving LB functions, with particular emphasis on AA metabolism, eicosanoid biosynthesis, and subsequent release of proinflammatory lipid mediators from these cells.
Highlights
Lipid droplets, called lipid bodies (LB) in inflammatory cells, are important cytoplasmic organelles
To analyze whether intracellular neutral lipid storage sites are formed during the maturation process, the mast cells (MC) were stained with Oil Red O (Fig. 1)
This study focuses on the characterization of cytoplasmic lipid bodies in mast cells during their phenotypic maturation from CD34+ progenitor cells derived from human are obtained in a well-defined cell population representing one of the two major human mast cell types [32]
Summary
Called lipid bodies (LB) in inflammatory cells, are important cytoplasmic organelles. The main proteins known to regulate the metabolism of the LB lipids are the members of the PAT protein family, mostly studied in adipocytes. This family includes five perilipins: perilipin 1 (PLIN1; formerly perilipin), perilipin 2 (PLIN2; formerly adipose differentiation-related protein), perilipin 3 (PLIN3; formerly tail-interacting protein of 47 kDa), perilipin 4 (PLIN4; formerly S3-12), and perilipin 5 (PLIN5; formerly lipid storage droplet protein 5) [13].
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