A vitellogenic‐like carboxypeptidase expressed by human macrophages is localized in endoplasmic reticulum and membrane ruffles

Abstract

Carboxypeptidase, vitellogenic-like (CPVL) is a serine carboxypeptidase of unknown function that was first characterized in human macrophages. Initial studies suggested that CPVL is largely restricted to the monocytic lineage, although it may also be expressed by cells outside the immune system. Here, we use a new monoclonal antibody to characterize the properties and localization of CPVL in human macrophages to elucidate a possible function for the protease. CPVL is up-regulated during the maturation of monocytes (MO) to macrophages, although the protein can be seen in both. In primary macrophages, CPVL is glycosylated with high mannose residues and colocalizes with markers for endoplasmic reticulum, while in MO it is more disperse and less clearly associated with endoplasmic reticulum. CPVL is highly expressed in lamellipodia and membrane ruffles, which also concentrate markers of the secretory pathway (MIP-1alpha and tumour necrosis factor-alpha) and major histocompatibility complex (MHC) class I and II molecules. CPVL can be seen on early latex bead and Candida albicans phagosomes, but it is not retained in the maturing phagosome, unlike MHC class I/II. CPVL has a mixed cytosolic and membrane-associated localization but is not detectable on the outer plasma membrane. We propose that CPVL may be involved in antigen processing, the secretory pathway and/or in actin remodelling and lamellipodium formation.

Identification of genes differentially expressed during larval molting and metamorphosis of Helicoverpa armigera

“…In addition, three kinds of carboxypeptidase vitellogenic-like genes ( cpvl ) were detected in the epidermis of feeding 5th instar larvae. Human cpvl is upregulated during the maturation of monocytes (MO) to macrophages, and is involved in antigen processing, the secretory pathway and/or in actin remodeling and lamellipodium formation [34,35]. Because these genes were detected in feeding 5th instar feeding larvae, they may play important roles in larval growth and development.…”

Fxna, a novel gene differentially expressed in the rat ovary at the time of folliculogenesis, is required for normal ovarian histogenesis

“…The structural characteristics of Fxna predict its existence as a membrane-bound protein, and our results demonstrate that in contrast to most peptidases expressed in reproductive organs (Fujiwara et al, 1999), Fxna is localized to the ER instead of the cell membrane. Previously described ER peptidases include endoplasmic reticulum aminopeptidase 1 (ERAP1) (Fruci et al, 2006), the related aminopeptidase leukocyte-derived arginine aminopeptidase (L-RAP, also called ERAP2) (Saveanu et al, 2005;Tanioka et al, 2003), and vitellogenic carboxypeptidase-like protein (Harris et al, 2006). The presence in Fxna of up to eight putative transmembrane domains resembles the hydropathy profile of site-2 protease (S2P), a zinc metallo-aminopeptidase required for the intramembranous proteolysis of sterol-regulatory-element-binding proteins (SREBPs) (Rawson et al, 1997).…”

Functional Characterization of a Putative Serine Carboxypeptidase in Vascular Smooth Muscle Cells

“…13 Whereas another serine carboxypeptidase enriched in macrophages does not appear to undergo cleavage, 23 CTSA is proteolytically processed to 32-and 20-kDa fragments, each of which harbors a portion of the catalytic triad. 8 Although SCPEP1 is cleaved into a 35-kDa protein, the precise boundaries of this cleavage product are currently unknown.…”