Heat shock protein 27 regulates neutrophil chemotaxis and exocytosis through two independent mechanisms.
The targets of the p38 MAPK pathway responsible for regulation of neutrophil chemotaxis and exocytosis are unknown. One target of this pathway is the actin-binding protein, heat shock protein 27 (Hsp27). Therefore, we tested the hypothesis that Hsp27 mediates p38 MAPK-dependent chemotaxis and exocytosis in human neutrophils through regulation of actin reorganization. Sequestration of Hsp27 by introduction of anti-Hsp27 Ab, but not an isotype Ab, inhibited fMLP-stimulated chemotaxis, increased cortical F-actin in the absence of fMLP stimulation, and inhibited fMLP-stimulated exocytosis. Pretreatment with latrunculin A prevented actin reorganization and the changes in fMLP-stimulated exocytosis induced by Hsp27 sequestration. To determine the role of Hsp27 phosphorylation, wild-type, phosphorylation-resistant, or phosphorylation-mimicking recombinant Hsp27 was introduced into neutrophils by electroporation. The phosphorylation-resistant mutant significantly reduced migration toward fMLP, whereas none of the Hsp27 proteins affected fMLP-stimulated or TNF-alpha-stimulated exocytosis or actin polymerization. Endogenous Hsp27 colocalized with F-actin in unstimulated and fMLP-stimulated neutrophils, whereas phosphorylated Hsp27 showed cytosolic localization in addition to colocalization with F-actin. Our results suggest that Hsp27 regulates neutrophil chemotaxis and exocytosis in an actin-dependent, phosphorylation-independent manner. Phosphorylation of Hsp27 regulates chemotaxis, but not exocytosis, independent of regulation of actin reorganization.
Jog
Neelakshi R
NR
Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, KY 40202, USA.
Jala
Venkatakrishna R
VR
Ward
Richard A
RA
Rane
Madhavi J
MJ
Haribabu
Bodduluri
B
McLeish
Kenneth R
KR
D000199:Actins / Q000276:immunology / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002633:Chemotaxis / Q000187:drug effects / Q000276:immunology*; D005089:Exocytosis / Q000187:drug effects / Q000276:immunology*; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology*; D018832:Molecular Chaperones; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000276:immunology* / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology / Q000276:immunology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000276:immunology; D053778:Thiazolidines / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D053778:Thiazolidines; D009240:N-Formylmethionine Leucyl-Phenylalanine; D048051:p38 Mitogen-Activated Protein Kinases; C037067:latrunculin A