TY - JOUR
T1 - Role of clathrin-mediated endocytosis of surfactant protein a by alveolar macrophages in intracellular signaling
AU - Moulakakis, Christina
AU - Stamme, Cordula
N1 - Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2009/3
Y1 - 2009/3
N2 - We recently provided evidence that anti-inflammatory macrophage activation, i.e., the inhibition of constitutive and signal-induced NF-κB activity by the pulmonary collectin surfactant protein (SP)-A, critically involves a promoted stabilization of IκB-α, the predominant inhibitor of NF-κB, via posttranscriptional mechanisms comprising the activation of atypical (a)PKCζ. SP-A uptake and degradation by alveolar macrophages (AMφ) occur in a receptor-mediated, clathrin-dependent manner. However, a mutual link between endocytosis of and signaling by SP-A remains elusive. The aim of this study was to investigate whether clathrin-mediated endocytosis (CME) of SP-A by AM is a prerequisite for its modulation of the IκB-α/NF- κB pathway. The inhibition of clathrin-coated pit (CCP) formation and clathrin-coated vesicle (CCV) formation/budding abrogates SP-A-mediated IκB-α stabilization and SP-A-mediated inhibition of LPS-induced NF-κB activation in freshly isolated rat AMφ, as determined by Western analysis, fluorescence-activated cell sorting, confocal microscopy, and EMSA. Actin depolymerization and inhibition of CCP formation further abolished SP-A-mediated inhibition of LPS-induced TNF-α release, as determined by ELISA. In addition, SP-A-induced atypical PKCζ activation was abolished by pretreatment of AMφ with CCV inhibitors as determined by in vitro immunocomplex kinase assay. Although CME is classically considered as a means to terminate signaling, our results demonstrate that SP-A uptake via CME by AMφ has to precede the initiation of SP-A signaling.
AB - We recently provided evidence that anti-inflammatory macrophage activation, i.e., the inhibition of constitutive and signal-induced NF-κB activity by the pulmonary collectin surfactant protein (SP)-A, critically involves a promoted stabilization of IκB-α, the predominant inhibitor of NF-κB, via posttranscriptional mechanisms comprising the activation of atypical (a)PKCζ. SP-A uptake and degradation by alveolar macrophages (AMφ) occur in a receptor-mediated, clathrin-dependent manner. However, a mutual link between endocytosis of and signaling by SP-A remains elusive. The aim of this study was to investigate whether clathrin-mediated endocytosis (CME) of SP-A by AM is a prerequisite for its modulation of the IκB-α/NF- κB pathway. The inhibition of clathrin-coated pit (CCP) formation and clathrin-coated vesicle (CCV) formation/budding abrogates SP-A-mediated IκB-α stabilization and SP-A-mediated inhibition of LPS-induced NF-κB activation in freshly isolated rat AMφ, as determined by Western analysis, fluorescence-activated cell sorting, confocal microscopy, and EMSA. Actin depolymerization and inhibition of CCP formation further abolished SP-A-mediated inhibition of LPS-induced TNF-α release, as determined by ELISA. In addition, SP-A-induced atypical PKCζ activation was abolished by pretreatment of AMφ with CCV inhibitors as determined by in vitro immunocomplex kinase assay. Although CME is classically considered as a means to terminate signaling, our results demonstrate that SP-A uptake via CME by AMφ has to precede the initiation of SP-A signaling.
UR - http://www.scopus.com/inward/record.url?scp=64249097642&partnerID=8YFLogxK
U2 - 10.1152/ajplung.90458.2008
DO - 10.1152/ajplung.90458.2008
M3 - Journal articles
C2 - 19136579
AN - SCOPUS:64249097642
SN - 1040-0605
VL - 296
SP - 430
EP - 441
JO - American Journal of Physiology - Lung Cellular and Molecular Physiology
JF - American Journal of Physiology - Lung Cellular and Molecular Physiology
IS - 3
ER -