marginal zone B- & B1-cell-specific protein; mesenteric estrogen-dependent adipose 7; MEDA-7; plasma cell-induced resident endoplasmic reticulum protein; plasma cell-induced resident ER protein; pERp1; proapoptotic caspase adapter protein (MZB1, MEDA7, PACAP, HSPC190)

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Function

associates with IgM heavy chain & light chains & promotes IgM assembly & secretion
may exert its effect by acting as a molecular chaperone or as an oxidoreductase (displays a low level of oxidoreductase activity)
isoform 2 may be involved in regulation of apoptosis
helps to diversify peripheral B-cell functions by regulating Ca+2 stores, antibody secretion & integrin activation
acts as a hormone-regulated adipokine/proinflammatory cytokine implicated in causing chronic inflammation, affecting cellular expansion & blunting insulin response in adipocytes
may have a role in the onset of insulin resistance
forms an interchain disulfide bond with IgM monomers
part of the ER chaperone complex, a multi-protein complex in the endoplasmic reticulum containing a large number of molecular chaperones which associates with unassembled incompletely folded immunoglobulin heavy chains (putative)
isoform 2 interacts with CASP2 & CASP9
interacts with HSP90B1 & PDIA3 (Ca+2-dependent)

belongs to the MZB1 family

widely expressed with highest levels in adult brain
expression is frequently lower in intestinal-type gastric cancer
down-regulated in primary B-cells early after ligand- stimulated activation
up-regulated in bacterial lipopolysaccharides (LPS)- stimulated peritoneal macrophages
in obese patients, more abundant in omental than in subcutaneous fat

↑ UniProt http://www.uniprot.org/uniprot/Q8WU39.html
↑ Bonfoco E, Li E, Kolbinger F, Cooper NR. Characterization of a novel proapoptotic caspase-2- and caspase-9-binding protein. J Biol Chem. 2001 Aug 3;276(31):29242-50. Epub 2001 May 11. PMID: https://www.ncbi.nlm.nih.gov/pubmed/11350957