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C D Funk

Publications and source records attributed to C D Funk.

At least 19 recordsLinked to original sources
PubMed2001

Prostaglandins and leukotrienes: advances in eicosanoid biology.

Prostaglandins and leukotrienes are potent eicosanoid lipid mediators derived from phospholipase-released arachidonic acid that are involved in numerous homeostatic biological functions and inflammation. They are generated by cyclooxygenase isozymes and 5-lipoxygenase, respectively, and their biosynthesis and actions are blocked by clinically relevant nonsteroidal anti-inflammatory drugs, the newer generation coxibs (selective inhibitors of cyclooxygenase-2), and leukotriene modifiers. The prime mode of prostaglandin and leukotriene action is through specific G protein-coupled receptors, many of which have been cloned recently, thus enabling specific receptor agonist and antagonist development. Important insights into the mechanisms of inflammatory responses, pain, and fever have been gleaned from our current understanding of eicosanoid biology.

Animals↗
PubMed2001

Molecular cloning and functional characterization of murine cysteinyl-leukotriene 1 (CysLT(1)) receptors.

We sought to clone and characterize the murine cysteinyl-leukotriene D(4) receptor (mCysLT(1)R) to complement our studies with leukotriene-deficient mice. A cDNA, cloned from trachea mRNA by reverse transcriptase-polymerase chain reaction, has two potential initiator ATG codons that would encode for polypeptides of 352 and 339 amino acids, respectively. These two potential forms, predicted to be seven transmembrane-spanning domain proteins, have 87% amino acid identity with the human CysLT(1) receptor (hCysLT(1)R). Membrane fractions of Cos-7 cells transiently expressing the short mCysLT(1)R demonstrated high affinity and specific binding for leukotriene D(4) (LTD(4), K(d) = 0.25 +/- 0.04 nM). In competition binding experiments, LTD(4) was the most potent competitor (K(i) = 0.8 +/- 0.2 nM) followed by LTE(4) and LTC(4) (K(i) = 86.6 +/- 24.5 and 100.1 +/- 17.1 nM, respectively) and LTB(4) (K(i) > 1.5 microM). Binding of LTD(4) was competitively inhibited by the specific CysLT(1) receptor antagonists MK-571 [(+)-3-(((3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl) ((3-(dimethylamino)-3-oxopropyl)thio)methyl)thio)propanoic acid], pranlukast (Onon), and zafirlukast (Accolate), while the CysLT(1)/CysLT(2) receptor antagonist BAY-u9773 [6(R)-(4'-carboxyphenylthio)-5(S)-hydroxy-7(E),9(E),11(Z),14(Z)-eicosatetrenoic acid] was 1000 times less potent than LTD(4). In transiently transfected HEK293-T cells expressing either the long or short form of mCysLT(1)R, LTD(4) induced an increase of intracellular calcium. In Xenopus laevis melanophores transiently expressing either isoform, LTD(4) induced the dispersion of pigment granules, consistent with the activation by LTD(4) of a G(alphaq) (calcium) pathway. Functional elucidation of mCysLT(1)R properties as described here will enable further experiments to clarify the selective role of LTD(4) in murine models of inflammation and asthma.

Aequorin↗
PubMed2001

The murine cysteinyl leukotriene 2 (CysLT2) receptor. cDNA and genomic cloning, alternative splicing, and in vitro characterization.

Two classes of cysteinyl leukotriene receptor, CysLT(1) and CysLT(2), have been identified and pharmacologically characterized in human tissues. Although the CysLT(1) receptor mediates the proinflammatory effects of leukotrienes in human asthma, the physiological roles of CysLT(2) receptor are not defined, and a suitable mouse model would be useful in delineating function. We report here the molecular cloning and characterization of the mouse CysLT(2) receptor (mCysLT(2)R) from heart tissue. mCysLT(2)R cDNA encodes a protein of 309 amino acids, truncated at both ends compared with the human ortholog (hCysLT(2)R). The gene resides on the central region of mouse chromosome 14 and is composed of 6 exons with the entire coding region located in the last exon. Two 5'-untranslated region splice variants were identified with the short form lacking exon 3 as the predominant transcript. Although the overall expression of mCysLT(2)R is very low, the highest expression was detected in spleen, thymus, and adrenal gland by ribonuclease protection assay, and discrete sites of expression in heart were observed by in situ hybridization. Intracellular calcium mobilization in response to cysteinyl leukotriene administration was detected in human embryonic kidney 293T cells transfected with recombinant mCysLT(2)R with a rank order of potency leukotriene C(4)(LTC(4) ) = LTD(4)>>LTE(4). [(3)H]LTD(4) binding to membranes expressing mCysLT(2)R could be effectively competed by LTC(4) and LTD(4) and only partially inhibited by LTE(4) and BAYu9773. The identification of mCysLT(2)R will be useful for establishing CysLT(2)R-deficient mice and determining novel leukotriene functions.

5' Untranslated Regions↗
PubMed2001

12/15-Lipoxygenase gene disruption attenuates atherogenesis in LDL receptor-deficient mice.

BACKGROUND: Human 15-lipoxygenase (LO) and its murine analogue 12/15-LO are capable of directly oxidizing esterified fatty acids in lipoproteins and phospholipids. Because these oxidized products possess atherogenic properties, it was suggested that LOs may be involved in enhancing atherogenesis. Previous in vivo tests of the role of LOs in atherogenesis animal models, however, have yielded conflicting results. METHODS AND RESULTS: Aiming to study the role of the 12/15-LO in murine atherogenesis, we crossed LDL-receptor-deficient mice (LDL-R(-/-)) with 12/15-LO-knockout mice and evaluated plaque formation 3 to 18 weeks after initiation of a high-fat diet. Atherosclerotic lesions were considerably reduced in the LDL-R/12/15-LO-double-knockout mice compared with LDL-R(-/-) mice at 3, 9, 12, and 18 weeks, at the aortic root as well as throughout the aorta. The cellular composition of plaques from mice deficient in 12/15-LO did not differ with respect to macrophage and T-lymphocyte content compared with plaques from 12/15-LO littermates. CONCLUSIONS: 12/15-LO plays a dominant role in promoting atherogenesis in LDL-R(-/-) mice.

Animals↗
PubMed2001

Absence of 12/15-lipoxygenase expression decreases lipid peroxidation and atherogenesis in apolipoprotein e-deficient mice.

BACKGROUND: The enzyme 12/15-lipoxygenase (12/15-LO) has been implicated in the oxidative modification of LDL. In a murine model, we tested the hypothesis that deletion of 12/15-LO decreases atherogenesis by reducing oxidant stress, as measured by 2 indices of lipid peroxidation: isoprostane generation and autoantibody formation to malondialdehyde (MDA)-LDL, an epitope of LDL formed as a result of oxidative modification. METHODS AND RESULTS: 12/15-LO-deficient (12/15-LO(-/-)) mice were crossed with apolipoprotein E-deficient (apoE(-/-)) mice. At 10 weeks of age, atherosclerotic lesion initiation was significantly delayed in the double-knockout mice. The rate of lesion progression was diminished at 8 and 12 months, and even at 15 months, lesion size was reduced 50% (P<0.0005) compared with control apoE(-/-) mice. The urinary and plasma levels of the specific isoprostane 8,12-iso-iPF(2alpha)-VI, as well as IgG autoantibodies against MDA-LDL, were significantly reduced in the double-deficient mice in parallel with decreased atherosclerosis at all time points from 10 weeks to 15 months of age compared with apoE(-/-) controls. CONCLUSIONS: Enzymatic action of 12/15-LO contributes significantly to atherosclerotic lesion initiation and propagation in this murine model. Strong positive correlations exist between lesion size, isoprostane levels, and MDA-LDL autoantibodies, providing in vivo evidence for an enzymatic (12/15-LO) component to lipid peroxidation and atherogenesis.

Animals↗
PubMed2001

12/15-lipoxygenase translocation enhances site-specific actin polymerization in macrophages phagocytosing apoptotic cells.

The enzyme 12/15-lipoxygenase (12/15-LO) introduces peroxyl groups in a position-specific manner into unsaturated fatty acids in certain cells, but the role of such enzymatic lipid peroxidation remains poorly defined. Here we report a novel function for 12/15-LO in mouse peritoneal macrophages. When macrophages were coincubated with apoptotic cells, the enzyme translocated from cytosol to the plasma membrane and was more extensively concentrated at sites where macrophages bound apoptotic cells, colocalizing with polymerized actin of emerging filopodia. Disruption of F-actin did not prevent the 12/15-LO translocation. In contrast, inhibition of the 12/15-LO activity, or utilization of genetically engineered macrophages in which the 12/15-LO gene has been disrupted, greatly reduced actin polymerization in phagocytosing macrophages. Lysates of 12/15-LO-deficient macrophages had significantly lower ability to promote in vitro actin polymerization than the lysates of wild type macrophages. These studies suggest that the 12/15-LO enzyme plays a major role in local control of actin polymerization in macrophages in response to interaction with apoptotic cells.

Actins↗
PubMed2001

IL-4 inhibits osteoclast formation through a direct action on osteoclast precursors via peroxisome proliferator-activated receptor gamma 1.

IL-4 is a pleiotropic immune cytokine secreted by activated T(H)2 cells that inhibits bone resorption both in vitro and in vivo. The cellular targets of IL-4 action as well as its intracellular mechanism of action remain to be determined. We show here that IL-4 inhibits receptor activator of NF-kappaB ligand-induced osteoclast differentiation through an action on osteoclast precursors that is independent of stromal cells. Interestingly, this inhibitory effect can be mimicked by both natural as well as synthetic peroxisome proliferator-activated receptor gamma1 (PPARgamma1) ligands and can be blocked by the irreversible PPARgamma antagonist GW 9662. These findings suggest that the actions of IL-4 on osteoclast differentiation are mediated by PPARgamma1, an interpretation strengthened by the observation that IL-4 can activate a PPARgamma1-sensitive luciferase reporter gene in RAW264.7 cells. We also show that inhibitors of enzymes such as 12/15-lipoxygenase and the cyclooxygenases that produce known PPARgamma1 ligands do not abrogate the IL-4 effect. These findings, together with the observation that bone marrow cells from 12/15-lipoxygenase-deficient mice retain sensitivity to IL-4, suggest that the cytokine may induce novel PPARgamma1 ligands. Our results reveal that PPARgamma1 plays an important role in the suppression of osteoclast formation by IL-4 and may explain the beneficial effects of the thiazolidinedione class of PPARgamma1 ligands on bone loss in diabetic patients.

Animals↗
PubMed2001

Role of 'platelet-type' 12-lipoxygenase in skin carcinogenesis.

Murine and human skin express an abundance of lipoxygenase isoforms whose functions are not understood. Substantial data have implicated a role for the 'platelet-type' 12-lipoxygenase (P-12LO) metabolite, 12(S)-hydroxy-eicosatetraenoic acid (12-HETE), in a variety of tumor functions. Using P-12LO deficient mice, we sought to examine the role of the P-12LO pathway in tumor initiation and progression. Two distinct genetic strains of P-12LO deficient and wild-type mice, B6/129 Sv and SENCAR, were evaluated in two-stage carcinogenesis experiments. Carcinoma incidence was significantly reduced in the P-12LO deficient mice of the B6/129 Sv background but not the SENCAR-backcrossed mice. In contrast, papilloma incidence was reduced on the SENCAR background but not in the B6/129 Sv strain mice. A separate experiment employing a complete carcinogenesis protocol failed to find any difference in papilloma or carcinoma incidence. Overall, these data suggest that the P-12LO pathway may contribute to tumor incidence and progression in two-stage, but not complete, carcinogenesis, depending on the genetic background.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

The N-terminal "beta-barrel" domain of 5-lipoxygenase is essential for nuclear membrane translocation.

5-Lipoxygenase is the key enzyme in the formation of leukotrienes, which are potent lipid mediators of asthma pathophysiology. This enzyme translocates to the nuclear envelope in a calcium-dependent manner for leukotriene biosynthesis. Eight green fluorescent protein (GFP)-lipoxygenase constructs, representing the major human and mouse enzymes within this family, were constructed and their cDNAs transfected into human embryonic kidney 293 cells. Of these eight lipoxygenases, only the 5-lipoxygenase was clearly nuclear localized and translocated to the nuclear envelope upon stimulation with the calcium ionophore. The N-terminal "beta -barrel" domain of 5-lipoxygenase, but not the catalytic domain, was necessary and sufficient for nuclear envelope translocation. The GFP-N-terminal 5-lipoxygenase domain translocated faster than GFP-5-lipoxygenase. beta-Barrel/catalytic domain chimeras with 12- and 15-lipoxygenase indicated that only the N-terminal domain of 5-lipoxygenase could carry out this translocation function. Mutations of iron atom binding ligands (His550 or deletion of C-terminal isoleucine) that disrupt nuclear localization do not alter translocation capacity indicating distinct determinants of nuclear localization and translocation. Moreover, data show that GFP-5-lipoxygenase beta-barrel containing constructs can translocate to the nuclear membrane whether cytoplasmic or nuclear localized. Thus, the predicted beta-barrel domain of 5-lipoxygenase may function like the C2 domain within protein kinase C and cytosolic phospholipase A(2) with unique determinants that direct its localization to the nuclear envelope.

Active Transport, Cell Nucleus↗
PubMed2001

Characterization of the murine epidermal 12/15-lipoxygenase.

The murine lipoxygenase (LO) family consists of at least seven members classified according to the HETE (hydroxyeicosatetraenoic acid) metabolite generated during arachidonic acid metabolism and the site of tissue expression. At present there are four 12-lipoxygenases that are functionally distinct, vary in cell and tissue distribution, catalytic activity and each are products of separate, linked genes. They are "platelet-type" 12-LO (P-12LO), "leukocyte-type" 12-LO (L-12LO), "epidermal-type" 12-LO (e-12LO) and the most recently discovered 12(R)-LO. In this report we characterize e-12LO, which was overexpressed in the baculovirus/insect cell expression system. The enzyme functions as a dual specificity 12/15-lipoxygenase with a 12-HETE/15-HETE product ratio of approximately 6:1 with arachidonic acid as substrate. Several other polyunsaturated fatty acids served as substrates for e-12LO such as gamma-linolenic, dihomo-gamma-linolenic and eicosapentaenoic acids. A green fluorescent protein/e-12LO fusion protein was localized to the cytosol of transfected HEK 293 cells. The e-12LO gene was expressed in mouse oocytes and early embryos. Western blot analysis revealed high level expression in postnatal day 3 mouse epidermal lysates. Together these data suggest that e-12LO plays a role in normal epidermal function and as yet an undiscovered role in early development.

Amino Acid Sequence↗
PubMed2001

Leukocyte-type 12-lipoxygenase-deficient mice show impaired ischemic preconditioning-induced cardioprotection.

To investigate the role of 12-lipoxygenase in preconditioning, we examined whether hearts lacking the "leukocyte-type" 12-lipoxygenase (12-LOKO) would be protected by preconditioning. In hearts from wild-type (WT) and 12-LOKO mice, left ventricular developed pressure (LVDP) and (31)P NMR were monitored during treatment (+/-preconditioning) and during global ischemia and reperfusion. Postischemic function (rate-pressure product, percentage of initial value) measured after 20 min of ischemia and 40 min of reperfusion was significantly improved by preconditioning in WT hearts (78 +/- 12% in preconditioned vs. 44 +/- 7% in nonpreconditioned hearts) but not in 12-LOKO hearts (47 +/- 7% in preconditioned vs. 33 +/- 10% in nonpreconditioned hearts). Postischemic recovery of phosphocreatine was significantly better in WT preconditioned hearts than in 12-LOKO preconditioned hearts. Preconditioning significantly reduced the fall in intracellular pH during sustained ischemia in both WT and 12-LOKO hearts, suggesting that attenuation of the fall in pH during ischemia can be dissociated from preconditioning-induced protection. Necrosis was assessed after 25 min of ischemia and 2 h of reperfusion using 2,3,5-triphenyltetrazolium chloride. In WT hearts, preconditioning significantly reduced the area of necrosis (26 +/- 4%) compared with nonpreconditioned hearts (62 +/- 10%) but not in 12-LOKO hearts (85 +/- 3% in preconditioned vs. 63 +/- 11% in nonpreconditioned hearts). Preconditioning resulted in a significant increase in 12(S)-hydroxyeicosatetraenoic acid in WT but not in 12-LOKO hearts. These data demonstrate that 12-lipoxygenase is important in preconditioning.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2000

Analysis of a nucleotide-binding site of 5-lipoxygenase by affinity labelling: binding characteristics and amino acid sequences.

5-Lipoxygenase (5LO) catalyses the first two steps in the biosynthesis of leukotrienes, which are inflammatory mediators derived from arachidonic acid. 5LO activity is stimulated by ATP; however, a consensus ATP-binding site or nucleotide-binding site has not been found in its protein sequence. In the present study, affinity and photoaffinity labelling of 5LO with 5'-p-fluorosulphonylbenzoyladenosine (FSBA) and 2-azido-ATP showed that 5LO bound to the ATP analogues quantitatively and specifically and that the incorporation of either analogue inhibited ATP stimulation of 5LO activity. The stoichiometry of the labelling was 1.4 mol of FSBA/mol of 5LO (of which ATP competed with 1 mol/mol) or 0.94 mol of 2-azido-ATP/mol of 5LO (of which ATP competed with 0.77 mol/mol). Labelling with FSBA prevented further labelling with 2-azido-ATP, indicating that the same binding site was occupied by both analogues. Other nucleotides (ADP, AMP, GTP, CTP and UTP) also competed with 2-azido-ATP labelling, suggesting that the site was a general nucleotide-binding site rather than a strict ATP-binding site. Ca(2+), which also stimulates 5LO activity, had no effect on the labelling of the nucleotide-binding site. Digestion with trypsin and peptide sequencing showed that two fragments of 5LO were labelled by 2-azido-ATP. These fragments correspond to residues 73-83 (KYWLNDDWYLK, in single-letter amino acid code) and 193-209 (FMHMFQSSWNDFADFEK) in the 5LO sequence. Trp-75 and Trp-201 in these peptides were modified by the labelling, suggesting that they were immediately adjacent to the C-2 position of the adenine ring of ATP. Given the stoichiometry of the labelling, the two peptide sequences of 5LO were probably near each other in the enzyme's tertiary structure, composing or surrounding the ATP-binding site of 5LO.

Adenosine Triphosphate↗
PubMed1999

Interleukin-4-dependent production of PPAR-gamma ligands in macrophages by 12/15-lipoxygenase.

The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a ligand-dependent nuclear receptor that has been implicated in the modulation of critical aspects of development and homeostasis, including adipocyte differentiation, glucose metabolism and macrophage development and function. PPAR-gamma is activated by a range of synthetic and naturally occurring substances, including antidiabetic thiazolidinediones, polyunsaturated fatty acids, 15-deoxy-delta prostaglandin J2 and components of oxidized low-density lipoprotein, such as 13-hydroxyoctadecadienoic acid (13-HODE) and 15-hydroxyeicosatetraenoic acid (15-HETE). However, the identities of endogenous ligands for PPAR-gamma and their means of production in vivo have not been established. In monocytes and macrophages, 13-HODE and 15-HETE can be generated from linoleic and arachidonic acids, respectively, by a 12/15-lipoxygenase that is upregulated by the TH2-derived cytokine interleukin-4. Here we show that interleukin-4 also induces the expression of PPAR-gamma and provide evidence that the coordinate induction of PPAR-gamma and 12/15-lipoxygenase mediates interleukin-4-dependent transcription of the CD36 gene in macrophages. These findings reveal a physiological role of 12/15-lipoxygenase in the generation of endogenous ligands for PPAR-gamma, and suggest a paradigm for the regulation of nuclear receptor function by cytokines.

Animals↗
PubMed1999

Resistance to type 1 diabetes induction in 12-lipoxygenase knockout mice.

Leukocyte 12-lipoxygenase (12-LO) gene expression in pancreatic beta cells is upregulated by cytotoxic cytokines like IL-1beta. Recent studies have demonstrated that 12-LO inhibitors can prevent glutamate-induced neuronal cell death when intracellular glutathione stores are depleted. Therefore, 12-LO pathway inhibition may prevent beta-cell cytotoxicity. To evaluate the role of 12-LO gene expression in immune-mediated islet destruction, we used 12-LO knockout (12-LO KO) mice. Male homozygous 12-LO KO mice and control C57BL/6 mice received 5 consecutive daily injections of low-dose streptozotocin to induce immune-mediated diabetes. Fasting serum glucose and insulin levels were measured at 7-day intervals, and the mice were followed up for 28 days. 12-LO KO mice were highly resistant to diabetes development compared with control mice and had higher serum insulin levels on day 28. Isolated pancreatic islets were treated with IL-1beta, TNF-alpha, and IFN-gamma for 18 hours. Glucose-stimulated insulin secretion in cytokine-treated islets from C57/BL6 mice decreased 54% from that of untreated islets. In marked contrast, the same cytokine mix led to only a 26% decrease in islets from 12-LO KO mice. Furthermore, cytokine-induced 12-hydroxyeicosatetraenoic acid (12-HETE) production was absent in 12-LO KO islets but present in C57/BL6 islets. Isolated peritoneal macrophages were stimulated for 48 hours with IFN-gamma + LPS and compared for nitrate/nitrite generation. 12-LO KO macrophages generated 50% less nitrate/nitrite when compared with C57BL/6 macrophages. In summary, elimination of leukocyte 12-LO in mice ameliorates low dose streptozotocin-induced diabetes by increasing islet resistance to cytokines and decreasing macrophage production of nitric oxide.

Animals↗
PubMed1999

Leukotriene binding, signaling, and analysis of HIV coreceptor function in mouse and human leukotriene B4 receptor-transfected cells.

The mouse leukotriene B4 receptor (m-BLTR) gene was cloned. Membrane fractions of human embryonic kidney 293 cells stably expressing m-BLTR demonstrated a high affinity and specific binding for leukotriene B4 (LTB4, Kd = 0.24 +/- 0.03 nM). In competition binding experiments, LTB4 was the most potent competitor (Ki = 0.23 +/- 0.05 nM) followed by 20-hydroxy-LTB4 (Ki = 1.1 +/- 0.2 nM) and by 6-trans-12-epi-LTB4 and LTD4 (Ki > 1 microM). In stably transfected Chinese hamster ovary cells, LTB4 inhibited forskolin-activated cAMP production and induced an increase of intracellular calcium, suggesting that this receptor is coupled to Gi- and Go-like proteins. In Xenopus laevis melanophores transiently expressing m-BLTR, LTB4 induced the aggregation of pigment granules, confirming the inhibition of cAMP production induced by LTB4. BLT receptors share significant sequence homology with chemokine receptors (CCR5 and CXCR4) that act as human immunodeficiency virus (HIV) coreceptors. However, among the 16 HIV/SIV strains tested, the human BLT receptor did not act as a coreceptor for virus entry into CD4-expressing cells based on infection and cell-cell fusion assays. In 5-lipoxygenase-deficient mice, the absence of leukotriene B4 biosynthesis did not detectably alter m-BLT receptor binding in membranes obtained from glycogen-elicited neutrophils. Isolation of the m-BLTR gene will form the basis of future experiments to elucidate the selective role of LTB4, as opposed to cysteinyl-leukotrienes, in murine models of inflammation.

Animals↗
PubMed1999

Role of decay-accelerating factor in regulating complement activation on the erythrocyte surface as revealed by gene targeting.

Decay-accelerating factor (DAF) is a glycosylphosphatidylinositol (GPI)-anchored membrane protein that inhibits both the classical and the alternative pathways of complement activation. DAF has been studied extensively in humans under two clinical settings: when absent from the erythrocytes of paroxysmal nocturnal hemoglobinuria (PNH) patients, who suffer from complement-mediated hemolytic anemia, and in transgenic pigs expressing human DAF, which have been developed to help overcome complement-mediated hyperacute rejection in xenotransplantation. Nevertheless, the exact role of DAF in regulating complement activation in vivo on the cell surface and the species specificity of this molecule remain to be fully characterized. To address these issues, we have used gene targeting to produce mice lacking GPI-anchored DAF. We found that erythrocytes from mice deficient in GPI-anchored DAF showed no increase in spontaneous complement activation in vivo but exhibited impaired regulation of zymosan-initiated bystander and antibody-triggered classical pathway complement activation in vitro, resulting in enhanced complement deposition. Despite a high level of C3 fixation, no homologous hemolysis occurred. It is noteworthy that GPI-linked DAF knockout erythrocytes, when tested with human and guinea pig sera, were more susceptible to heterologous complement lysis than were normal erythrocytes. These results suggest that DAF is capable of regulating homologous as well as heterologous complement activation via the alternative or the classical pathway. They also indicate that DAF deficiency alone is not sufficient to cause homologous hemolysis. In contrast, when the assembly of the membrane-attack complex is not properly regulated, as in the case of heterologous complement activation or in PNH patients, impaired erythrocyte DAF activity and enhanced C3 deposition could lead to increased hemolytic reaction.

Animals↗