TY - JOUR
T1 - Caveolin-1 and caveolin-2 expression in mouse macrophages
T2 - High density lipoprotein 3-stimulated secretion and a lack of significant subcellular co-localization
AU - Gargalovic, Peter
AU - Dory, Ladislav
PY - 2001/7/13
Y1 - 2001/7/13
N2 - Evidence for caveolin expression in macrophages is scarce and conflicting. We therefore examined caveolin-1 and caveolin-2 expression in resident and thioglycollate-elicited mouse peritoneal macrophages (tg-MPM) and in the J774 mouse macrophage cell line by RT-PCR, ribonuclease protection assay, immunoblotting, and immunofluorescence. We found that relative to 3T3 cells, resident MPM and tg-MPM express low amounts of caveolin-1 (45 and 15% of those in 3T3 fibroblasts, respectively), while J774.A1 cells do not express any. Caveolin-2, on the other hand, is expressed in all cells examined, with highest expression in tg-MPM and the lowest in J774 cells. The relative levels of caveolin expression in the various cells correspond well with their respective mRNA levels, as measured by ribonuclease protection assay. Caveolin-1, present primarily on the cell surface, does not co-localize significantly with caveolin-2, which is present primarily in the Golgi compartment in all macrophages studied. Loading of tg-MPM with cholesterol or variations in unesterified cholesterol content appear to have little effect on the level of caveolin-1 or -2 expression or their distribution. Stimulation of cholesterol efflux by HDL3 leads to caveolin-1 and caveolin-2 secretion to the cell culture medium, a process not detected in the absence of HDL3. The lack of significant co-localization of the two caveolin isoforms in primary macrophages and their secretion in the presence of HDL3 provides an interesting and physiologically relevant model system to study additional aspects of caveolin function.
AB - Evidence for caveolin expression in macrophages is scarce and conflicting. We therefore examined caveolin-1 and caveolin-2 expression in resident and thioglycollate-elicited mouse peritoneal macrophages (tg-MPM) and in the J774 mouse macrophage cell line by RT-PCR, ribonuclease protection assay, immunoblotting, and immunofluorescence. We found that relative to 3T3 cells, resident MPM and tg-MPM express low amounts of caveolin-1 (45 and 15% of those in 3T3 fibroblasts, respectively), while J774.A1 cells do not express any. Caveolin-2, on the other hand, is expressed in all cells examined, with highest expression in tg-MPM and the lowest in J774 cells. The relative levels of caveolin expression in the various cells correspond well with their respective mRNA levels, as measured by ribonuclease protection assay. Caveolin-1, present primarily on the cell surface, does not co-localize significantly with caveolin-2, which is present primarily in the Golgi compartment in all macrophages studied. Loading of tg-MPM with cholesterol or variations in unesterified cholesterol content appear to have little effect on the level of caveolin-1 or -2 expression or their distribution. Stimulation of cholesterol efflux by HDL3 leads to caveolin-1 and caveolin-2 secretion to the cell culture medium, a process not detected in the absence of HDL3. The lack of significant co-localization of the two caveolin isoforms in primary macrophages and their secretion in the presence of HDL3 provides an interesting and physiologically relevant model system to study additional aspects of caveolin function.
UR - http://www.scopus.com/inward/record.url?scp=0035854831&partnerID=8YFLogxK
U2 - 10.1074/jbc.M011291200
DO - 10.1074/jbc.M011291200
M3 - Article
C2 - 11316799
AN - SCOPUS:0035854831
SN - 0021-9258
VL - 276
SP - 26164
EP - 26170
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 28
ER -