Cholesteryl ester loading of mouse peritoneal macrophages is associated with changes in the expression or modification of specific cellular proteins, including increase in an alpha-enolase isoform.

Abstract

This report explores the hypothesis that massive cholesteryl ester (CE) accumulation in macrophages, such as that occurring in atheroma foam cells, results in changes in the expression or modification of specific cellular proteins. Two-dimensional (2-D) gel electrophoretic patterns of metabolically labeled cellular proteins from mouse peritoneal macrophages that were loaded with CE (through incubation with acetylated low density lipoprotein [acetyl-LDL] for 4 days) were compared with those of control macrophages. Densitometric analysis of 2-D gel autoradiograms from the cell lysates revealed statistically significant changes in seven cellular proteins (five decreases and two increases). The changes in protein expression (foam cell versus control) ranged from a 458±164% (p<0.001) increase to a 35±34% (p<0.001) decrease (n=U). Incubation of macrophages with /3-very low density lipoprotein, which also increased the CE content of macrophages (albeit to a lesser extent than acetyl-LDL), resulted in changes in five of the seven proteins. In contrast, incubation of cells with LDL, fucoidan, or latex beads, none of which caused CE accumulation, did not lead to significant changes in four of these five proteins. One of these four proteins, which increased fourfold to fivefold in foam cells (Af r =49,00O; isoelectric point of 6.8), was purified by preparative 2-D gel electrophoresis. Internal amino acid sequence of cyanogen bromide fragments of this protein as well as Western blot analysis identified this protein as an isoform of er-enolase. The increased expression of this or-enolase isoform, which was seen as early as day 2 of acetyl-LDL incubation of the macrophages, was diminished by including an inhibitor of cholesterol esterification during the acetyl-LDL incubation period. In conclusion, macrophage foam cell formation is associated with distinct changes in protein expression, including a marked increase in an isoform of a-enolase, suggesting a specific biological adaptation to CE loading. (Arteriosclerosis and Thrombosis 1993;13:264-275

Biochemical characterization of the mouse muscle-specific enolase: developmental changes in electrophoretic variants and selective binding to other proteins

“…The existence of electrophoretic variants has already been reported for the purified rabbit β-enolase [38] and for the α-enolase present in mouse macrophages [40]. We find that the endogenous β-enolase subunit obtained from various adult mouse muscle extracts (heart, gastrocnemius and soleus muscles) always exhibits the same heterogeneous pattern, with two variants of identical size.…”

Decoding Serological Response to Candida Cell Wall Immunome into Novel Diagnostic, Prognostic, and Therapeutic Candidates for Systemic Candidiasis by Proteomic and Bioinformatic Analyses

“…This raises the hypothesis of a specific mechanism of Candida enolase processing, as reported in other eukaryotic enolases (85)(86)(87), during cell wall biogenesis and prompts the proposal that the antibodies involved in protection against SC might be directed against specific epitopes or antigenic motifs of the Candida surface-associated form of enolase. Their identification, which is now under way, could provide a rationale for the design of novel immunotherapy-or vaccine-based strategies to prevent and control SC.…”

The Role of an Enolase‐Related Molecule in Plasminogen Binding to Cells

“…Within a-enolase, a hydrophobic domain spanning amino acid residues 33 -44 might serve as an internal signal sequence, as it is similar in size to the H1 hydrophobic region of PAI-2 that contributes to the PAI-2 secretion signal (von Heijne et al, 1991). Membrane association of a-enolase might be mediated by postranslational acylation, as foam cell macrophages have been shown to incorporate radiolabeled myristate and palmitate into a-enolase (Bottalico et al, 1993). It is of interest to note that three other candidate plasmin(ogen) receptors which have been described recently, streptococcal glyceraldehyde-3-phosphate dehydrogenase (Lottenberg et al, 1992), endothelial cell annexin-11-related molecule (Hajjar and Jacovina, 1993) and amphoterin (Parkkinen and Rauvala, 1991;Meirenmies et al, 1991) lack cleavable signal sequences as well.…”