 |
|
|
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
134 a.a.
133 a.a.
129 a.a.
_CA
Key reference
Full text J Immunol 180:2329-2338 (2008) PubMed id: 18250442
C1q binds phosphatidylserine and likely acts as a multiligand-bridging molecule in apoptotic cell recognition. H.Païdassi, P.Tacnet-Delorme, V.Garlatti, C.Darnault, B.Ghebrehiwet, C.Gaboriaud, G.J.Arlaud, P.Frachet. ABSTRACT
Efficient apoptotic cell clearance is critical for maintenance of tissue homeostasis, and to control the immune responses mediated by phagocytes. Little is known about the molecules that contribute "eat me" signals on the apoptotic cell surface. C1q, the recognition unit of the C1 complex of complement, also senses altered structures from self and is a major actor of immune tolerance. HeLa cells were rendered apoptotic by UV-B treatment and a variety of cellular and molecular approaches were used to investigate the nature of the target(s) recognized by C1q. Using surface plasmon resonance, C1q binding was shown to occur at early stages of apoptosis and to involve recognition of a cell membrane component. C1q binding and phosphatidylserine (PS) exposure, as measured by annexin V labeling, proceeded concomitantly, and annexin V inhibited C1q binding in a dose-dependent manner. As shown by cosedimentation, surface plasmon resonance, and x-ray crystallographic analyses, C1q recognized PS specifically and avidly (K(D) = 3.7-7 x 10(-8) M), through multiple interactions between its globular domain and the phosphoserine group of PS. Confocal microscopy revealed that the majority of the C1q molecules were distributed in membrane patches where they colocalized with PS. In summary, PS is one of the C1q ligands on apoptotic cells, and C1q-PS interaction takes place at early stages of apoptosis, in newly organized membrane patches. Given its versatile recognition properties, these data suggest that C1q has the unique ability to sense different markers which collectively would provide strong eat me signals, thereby allowing efficient apoptotic cell removal.
Literature references that cite this PDB file's key reference
PubMed id Reference
19919576 D.A.Fraser, K.Pisalyaput, and A.J.Tenner (2010).
C1q enhances microglial clearance of apoptotic neurons and neuronal blebs, and modulates subsequent inflammatory cytokine production.J Neurochem, 112, 733-743.
19302245 B.Gullstrand, U.Mårtensson, G.Sturfelt, A.A.Bengtsson, and L.Truedsson (2009).
Complement classical pathway components are all important in clearance of apoptotic and secondary necrotic cells.Clin Exp Immunol, 156, 303-311.
19321608 J.Tian, Z.Xu, J.S.Smith, S.E.Hofherr, M.A.Barry, and A.P.Byrnes (2009).
Adenovirus activates complement by distinctly different mechanisms in vitro and in vivo: indirect complement activation by virions in vivo.J Virol, 83, 5648-5658. 19763574 L.Walter, and H.Neumann (2009).
Role of microglia in neuronal degeneration and regeneration.Semin Immunopathol, 31, 513-525. The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time.
