Tilmann Laufs

Visual performance of the vertebrate eye requires large amounts of oxygen, and thus the retina is one of the highest oxygen-consuming tissues of the body. Here we show that neuroglobin, a neuron-specific respiratory protein distantly related to hemoglobin and myoglobin, is present at high amounts in the mouse retina (approximately 100 microm). The estimated concentration of neuroglobin in the retina is thus about 100-fold higher than in the brain and is in the same range as that of myoglobin in the muscle. Neuroglobin is expressed in all neurons of the retina but not in the retinal pigment epithelium. Neuroglobin mRNA was detected in the perikarya of the nuclear and ganglion layers of the neuronal retina, whereas the protein was present mainly in the plexiform layers and in the ellipsoid region of photoreceptor inner segment. The distribution of neuroglobin correlates with the subcellular localization of mitochondria and with the relative oxygen demands, as the plexiform layers and the inner segment consume most of the retinal oxygen. These findings suggest that neuroglobin supplies oxygen to the retina, similar to myoglobin in the myocardium and the skeletal muscle.

Cytoglobin is a recently discovered vertebrate globin distantly related to myoglobin, and its function is unknown. Here we present the first detailed analysis of the distribution and expression of cytoglobin. Northern and Western blotting experiments show the presence of cytoglobin mRNA and protein in a broad range of tissues. Quantitative PCR demonstrates an up-regulation of cytoglobin mRNA levels in rat heart and liver under hypoxic conditions (22 and 44 h of 9% oxygen). Immunofluorescence studies with three antibodies directed against different epitopes of the protein consistently show cytoglobin in connective tissue fibroblasts as well as in hepatic stellate cells. Cytoglobin is also present in chondroblasts and osteoblasts and shows a decreased level of expression upon differentiation to chondrocytes and osteocytes. Cytoglobin is located in the cytoplasm of these cell types. Evidence against an exclusively nuclear localization of cytoglobin, as recently proposed, is also provided by transfection assays with green fluorescent protein fusion constructs, which demonstrates the absence of an active nuclear import. The differential expression of cytoglobin argues against a general respiratory function of this molecule, but rather indicates a connective tissue-specific function. We hypothesize that cytoglobin may be involved in collagen synthesis. Cytoglobin expression was also observed in some neuronal subpopulations of the central and the peripheral nervous systems. Surprisingly, cytoglobin is localized in both the cytoplasm and nucleus of neurons, indicating a possible additional role of this protein in neuronal tissues. Cytoglobin is a recently discovered vertebrate globin distantly related to myoglobin, and its function is unknown. Here we present the first detailed analysis of the distribution and expression of cytoglobin. Northern and Western blotting experiments show the presence of cytoglobin mRNA and protein in a broad range of tissues. Quantitative PCR demonstrates an up-regulation of cytoglobin mRNA levels in rat heart and liver under hypoxic conditions (22 and 44 h of 9% oxygen). Immunofluorescence studies with three antibodies directed against different epitopes of the protein consistently show cytoglobin in connective tissue fibroblasts as well as in hepatic stellate cells. Cytoglobin is also present in chondroblasts and osteoblasts and shows a decreased level of expression upon differentiation to chondrocytes and osteocytes. Cytoglobin is located in the cytoplasm of these cell types. Evidence against an exclusively nuclear localization of cytoglobin, as recently proposed, is also provided by transfection assays with green fluorescent protein fusion constructs, which demonstrates the absence of an active nuclear import. The differential expression of cytoglobin argues against a general respiratory function of this molecule, but rather indicates a connective tissue-specific function. We hypothesize that cytoglobin may be involved in collagen synthesis. Cytoglobin expression was also observed in some neuronal subpopulations of the central and the peripheral nervous systems. Surprisingly, cytoglobin is localized in both the cytoplasm and nucleus of neurons, indicating a possible additional role of this protein in neuronal tissues. Globins are small heme-containing proteins that have the ability to bind O2 and other gaseous ligands (1Dickerson R.E. Geis I. Hemoglobin: Structure, Function, Evolution, and Pathology. Benjamin/Cummings, Menlo Park, CA1983Google Scholar). Most globins efficiently capture and deliver O2, thus sustaining the aerobic metabolism of the respiratory chain (2Hardison R.C. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 5675-5679Crossref PubMed Scopus (290) Google Scholar, 3Hardison R.C. J. Exp. Biol. 1998; 201: 1099-1117Crossref PubMed Google Scholar, 4Merx M.W. Flögel U. Stumpe T. Gödecke A. Decking U.K. Schrader J. FASEB J. 2002; 15: 1077-1079Crossref Scopus (91) Google Scholar, 5Wittenberg B.A. Wittenberg J.B. Annu. Rev. Physiol. 1989; 51: 857-878Crossref PubMed Scopus (410) Google Scholar, 6Wittenberg J.B. Wittenberg B.A. J. Exp. Biol. 1993; 206: 2011-2020Crossref Scopus (396) Google Scholar). Some globins may also act as enzymes utilizing molecular O2 in oxidation reactions (7Minning D.M. Gow A.J. Bonaventura J. Braun R. Dewhirst M. Goldberg D.E. Stamler J.S. Nature. 1999; 401: 497-502Crossref PubMed Scopus (183) Google Scholar, 8Flögel U. Merx M.W. Gödecke A. Decking U.K. Schrader J. Proc. Natl. Acad. Sci. U. S. A. 2001; 98: 735-740Crossref PubMed Scopus (382) Google Scholar). Vertebrates harbor four distinct globin types that differ in tissue distribution and function. The heterotetrameric hemoglobin facilitates the transport of O2 in the red blood cells of the circulatory system (1Dickerson R.E. Geis I. Hemoglobin: Structure, Function, Evolution, and Pathology. Benjamin/Cummings, Menlo Park, CA1983Google Scholar). The myocytes of the cardiac and striated muscles contain myoglobin, a monomeric protein that enhances O2 diffusion to the mitochondria of this metabolically highly active tissue and acts as a temporal O2 store (4Merx M.W. Flögel U. Stumpe T. Gödecke A. Decking U.K. Schrader J. FASEB J. 2002; 15: 1077-1079Crossref Scopus (91) Google Scholar, 5Wittenberg B.A. Wittenberg J.B. Annu. Rev. Physiol. 1989; 51: 857-878Crossref PubMed Scopus (410) Google Scholar, 6Wittenberg J.B. Wittenberg B.A. J. Exp. Biol. 1993; 206: 2011-2020Crossref Scopus (396) Google Scholar). Myoglobin may also act as an NO dioxygenase (8Flögel U. Merx M.W. Gödecke A. Decking U.K. Schrader J. Proc. Natl. Acad. Sci. U. S. A. 2001; 98: 735-740Crossref PubMed Scopus (382) Google Scholar). A respiratory function has also been attributed to neuroglobin (Ngb), 1The abbreviations used are: Ngb, neuroglobin; Cygb, cytoglobin; ELISA, enzyme-linked immunosorbent assay; GFP, green fluorescent protein; HSCs, hepatic stellate cells; PBS, phosphate-buffered saline; ROS, reactive oxygen species; RT, reverse transcription; EST, expressed sequence tag. a recently described vertebrate monomeric globin (9Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar) that is expressed in neurons of the central and peripheral nervous systems (9Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar, 10Reuss S. Saaler-Reinhardt S. Weich B. Wystub S. Reuss M.H. Burmester T. Hankeln T. Neuroscience. 2002; 115: 645-656Crossref PubMed Scopus (166) Google Scholar, 11Wystub S. Laufs T. Schmidt M. Burmester T. Maas U. Saaler-Reinhardt S. Hankeln T. Reuss S. Neurosci. Lett. 2003; 346: 114-116Crossref PubMed Scopus (111) Google Scholar). Ngb is also present in endocrine tissues (10Reuss S. Saaler-Reinhardt S. Weich B. Wystub S. Reuss M.H. Burmester T. Hankeln T. Neuroscience. 2002; 115: 645-656Crossref PubMed Scopus (166) Google Scholar), and a particularly high Ngb concentration was observed in the mammalian retina (12Schmidt M. Gieβl A. Laufs T. Hankeln T. Wolfrum U. Burmester T. J. Biol. Chem. 2003; 278: 1932-1935Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar). Most recently, cytoglobin (Cygb) has been identified as the fourth member of the vertebrate globin family. Cygb has been identified in the expressed sequence tag (EST) databases from mouse, man, and zebrafish and was found to be expressed in a broad range of mammalian tissues (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar, 14Trent III, J.T. Hargrove M.S. J. Biol. Chem. 2002; 277: 19538-19545Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar). In an independent study, Kawada et al. (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar) had characterized the rat homologue of Cygb as a heme protein that shows enhanced expression in the stellate cells of the fibrotic liver, thus dubbing it “stellate cell activation-associated protein” or STAP (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, 16Asahina K. Kawada N. Kristensen D.B. Nakatani K. Seki S. Shiokawa M. Tateno C. M. Yoshizato K. 2002; PubMed Scopus Google Scholar). Cygb O2 the of the heme III, J.T. Hargrove M.S. J. Biol. Chem. 2002; 277: 19538-19545Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar, N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, 16Asahina K. Kawada N. Kristensen D.B. Nakatani K. Seki S. Shiokawa M. Tateno C. M. Yoshizato K. 2002; PubMed Scopus Google Scholar, Kawada N. Yoshizato K. S. Y. 2003; PubMed Scopus Google Scholar, S. A. J. Burmester T. Hankeln M. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). to some Ngb and some other globins S. III, J.T. Hargrove M.S. J. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar), Cygb a of the in the III, J.T. Hargrove M.S. J. Biol. Chem. 2002; 277: 19538-19545Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar, Kawada N. Yoshizato K. S. Y. 2003; PubMed Scopus Google Scholar, S. A. J. Burmester T. Hankeln M. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). Cygb has the of sequence observed the vertebrate with and Cygb in of the (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar). that Cygb and a which is distinct from neuroglobin and hemoglobin and from a globin (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar, A. M. A. S. Hankeln T. Burmester T. 2002; PubMed Scopus Google Scholar). Cygb is globins and of the is to both the and the the globin of and involved in O2 are in the Cygb protein A. M. A. S. Hankeln T. Burmester T. 2002; PubMed Scopus Google Scholar, S. A. Burmester T. Hankeln T. M. 2003; PubMed Scopus Google Scholar). In to the and of the of the and the mammalian Cygb contain an of the to the of the is in and may have been in (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar). The role of Cygb in the vertebrate metabolism is have been (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar, 14Trent III, J.T. Hargrove M.S. J. Biol. Chem. 2002; 277: 19538-19545Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar, N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, A. M. A. S. Hankeln T. Burmester T. 2002; PubMed Scopus Google Scholar, I. S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). to in the Cygb may O2 diffusion to the Cygb may also act as a protein that in O2 cells from reactive oxygen some other as NO or A. M. A. S. Hankeln T. Burmester T. 2002; PubMed Scopus Google Scholar). In of these the of Cygb function a detailed of its localization in different and cells. the are in of and Cygb distribution (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, 16Asahina K. Kawada N. Kristensen D.B. Nakatani K. Seki S. Shiokawa M. Tateno C. M. Yoshizato K. 2002; PubMed Scopus Google Scholar, I. S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). We a detailed Cygb localization and its by used in this under conditions with and and experiments to a that was by the The with and with of phosphate-buffered with of was a of with of in J. PubMed Scopus Google Scholar). The was to tissues and h in the and in phosphate-buffered in in with with a of in under conditions of was by the or 44 h in a which was with a 9% The by of of and liver tissues and in antibodies in against that had been to of and Cygb The antibodies are directed against the of the or of the or of the of the antibodies was from the the to a the and in with immunosorbent by h of with of Cygb in The h with in and three with with was The three with and with a in additional the was by in in the was by of and the was Western tissues in and with an of the protein of to a was protein to h by h with in The with in The four in and with the with in The in as and was with and as of with or h with in The with antibodies to in in the The in and in the with the to in The as described and in In some the was to the to the The an with a the which was also used to and and to Northern Northern of mRNA was under conditions with a Cygb by conditions The was h an and of of Cygb and the green fluorescent protein the Cygb was first with to and the and and the The PCR with the enzymes and and which contain the enhanced green fluorescent We four different and in which the are to and an additional the and to an of the globin protein fusion and by the was of cells and cells in with of and in a The to transfection cells a of the of of was used with of to the cells to the was and the h transfection in with R. Biol. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar) a with a an system of a with a and from rat was the and an The hypoxic and the a of four The hypoxic was a of The was with or reactions reverse we used reverse and an We the of to of Cygb expression was by a and a by the The we used and The was the and was to the of the the by the we also used the and in a an we used of the in a was to by of of In PCR we thus used the of that is to of of Cygb was the PCR The concentration PCR was both and the concentration was The was the of the by and The was in a and the the of by in a range from to to the of the was by the of expression of the hypoxic that of the the of or expression in hypoxic was by the of the of and The of the was by the antibodies that are directed against different Cygb in by the antibodies with Cygb in Western blotting and in The was by of the antibodies with a of Cygb, a with the of the antibodies in was observed with the fourth The antibodies tissues by Western antibodies and the of in which is the as the protein The antibodies are directed against from the globin and the The additional observed in the Western in some tissues and by of the with Cygb the of the Cygb is and was by and directed against the or reactions in Western of Cygb mRNA and in presence of Cygb mRNA in a broad range of tissues was by Northern blotting a we Cygb different levels in The Cygb mRNA a of which well with the from and of with antibodies Cygb protein to be present in distinct cell In the liver, was observed in the small hepatic stellate cells which are the A and In fibroblasts the connective tissue in the of blood are with the was of the antibodies with the was observed in as well as and red blood cells. Cygb was found in the cytoplasm of the HSCs, was of the The fibroblasts with the Cygb antibodies in and was observed in the connective tissue of the that the of the In the of the of the cells found to be which we to be the active in the chondrocytes Cygb was In the the fibroblasts was present in fibroblasts of the Cytoglobin expression was also observed in fibroblasts The osteoblasts and the of the both with the with the a in the in the and was to and the and was also present in and of the or the of these cells was with of the Most other cell types of these as the cells in the and the and the cells of the and the cells in the heart or the show that was to be we found the neurons of the in the to Cygb in these cells Cygb was found in both the cytoplasm the and the The of this is by the that in the fibroblasts is exclusively present in the Cygb was also found in the central nervous neurons of the The and from the in the neurons found in but to of the of A was found in the a of neurons in and the was present in the cell and and in cell to in the show of Cygb by localization of Cygb was by Cygb and GFP, and these cell the distribution of the fluorescent upon expression of the fusion as well as and with and a Cygb and with the transfection and was the cytoplasm and nucleus which argues against a nuclear of is that the nuclear is to diffusion of the fusion protein the The fusion protein Cygb is in the range of the nuclear Cygb mRNA under expression level of Cygb in heart and liver was by which had been in or to oxygen or 44 Quantitative experiments an up-regulation of Cygb mRNA in both under hypoxic In rat Cygb mRNA was by a of h and by 44 h We also observed a and a expression in rat liver or 44 The up-regulation of Cygb under is the the mRNA expression was in heart in liver the Northern globins are the proteins in of and Cygb was discovered recently as the fourth member of the vertebrate globin (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar, 14Trent III, J.T. Hargrove M.S. J. Biol. Chem. 2002; 277: 19538-19545Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar, N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar). Cygb have been A. M. A. S. Hankeln T. Burmester T. 2002; PubMed Scopus Google Scholar), but its role in metabolism is (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar, 14Trent III, J.T. Hargrove M.S. J. Biol. Chem. 2002; 277: 19538-19545Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar, N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, I. S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). of Cygb and was observed to be expressed in the of rat and liver (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, 16Asahina K. Kawada N. Kristensen D.B. Nakatani K. Seki S. Shiokawa M. Tateno C. M. Yoshizato K. 2002; PubMed Scopus Google Scholar). Here we show that Cygb is also present in cells that the connective and by the chondrocytes and cells. cell types have a as chondrocytes as well as from fibroblasts and to and Scholar). The of the is a of J. Physiol. Physiol. 2000; PubMed Google Scholar), it is that and fibroblasts are related of the M. J. Biol. 1998; PubMed Scopus Google Scholar). Cygb expression was found in distinct cell of the central and the peripheral nervous systems. these well with the presence of Cygb in a broad range of tissues and (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar, 14Trent III, J.T. Hargrove M.S. J. Biol. Chem. 2002; 277: 19538-19545Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar, 16Asahina K. Kawada N. Kristensen D.B. Nakatani K. Seki S. Shiokawa M. Tateno C. M. Yoshizato K. 2002; PubMed Scopus Google Scholar). three antibodies that against different Cygb as well as by tissue and we consistently identified the Cygb protein to be localized in the cytoplasm of distinct cell from the tissues. In the of the antibodies and thus the of by which In a et al. I. S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar) the that Cygb is an exclusively nuclear which is present in cells from a broad range of tissues. both and distribution of Cygb was to be distinct from these Cygb to be localized in the of we observed Cygb in the liver in the cytoplasm of and are in with independent studies rat and liver that identified Cygb in the cytoplasm of (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, 16Asahina K. Kawada N. Kristensen D.B. Nakatani K. Seki S. Shiokawa M. Tateno C. M. Yoshizato K. 2002; PubMed Scopus Google Scholar). experiments (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar) provided against the presence of Cygb in this cell The found Cygb in HSCs, which with against an nuclear localization of Cygb was provided by the experiments that fusion constructs, which show active transport of the fusion protein the A. T. 1998; PubMed Scopus Google Scholar) Cygb to be a protein is in the range as that myoglobin, a protein of the of and with independent (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, 16Asahina K. Kawada N. Kristensen D.B. Nakatani K. Seki S. Shiokawa M. Tateno C. M. Yoshizato K. 2002; PubMed Scopus Google Scholar), we that Cygb is a protein in fibroblasts and we the of et al. I. S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar), which we to be the of a of with a nuclear In to the in the Cygb was found in both the cytoplasm and of some neurons in the peripheral and central nervous systems. The of this is by the that three antibodies used which be by with the The differential localization of Cygb in neurons fibroblasts and related cells is and the of a that the active or diffusion of Cygb from the cytoplasm the be by a role of Cygb in neurons by the that conditions are to the or the the Cygb of Cygb function the and distribution of the protein Cygb is found in distinct cell that in to the and cells B.A. Wittenberg J.B. Annu. Rev. Physiol. 1989; 51: 857-878Crossref PubMed Scopus (410) Google Scholar, 6Wittenberg J.B. Wittenberg B.A. J. Exp. Biol. 1993; 206: 2011-2020Crossref Scopus (396) Google Scholar, T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar, 10Reuss S. Saaler-Reinhardt S. Weich B. Wystub S. Reuss M.H. Burmester T. Hankeln T. Neuroscience. 2002; 115: 645-656Crossref PubMed Scopus (166) Google Scholar, 11Wystub S. Laufs T. Schmidt M. Burmester T. Maas U. Saaler-Reinhardt S. Hankeln T. Reuss S. Neurosci. Lett. 2003; 346: 114-116Crossref PubMed Scopus (111) Google Scholar, M. Gieβl A. Laufs T. Hankeln T. Wolfrum U. Burmester T. J. Biol. Chem. 2003; 278: 1932-1935Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar), with high and thus oxygen a general role of Cygb in O2 diffusion to the respiratory chain of the as was recently (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar, N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar, Kawada N. Yoshizato K. S. Y. 2003; PubMed Scopus Google Scholar), a role of Cygb as that upon conditions may be are also to with a function of Cygb in oxygen I. S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar), is an be to the cell and some neuronal Kawada et al. (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar) that Cygb may the from reactive oxygen which are to be by Exp. 1999; PubMed Scopus Google Scholar). to the of is that cells are particularly to the other it is to that the role of Cygb in and is to collagen synthesis. O2 and in the cell types that is that Cygb molecular oxygen to the an dioxygenase that O2 the of in the T. R. J. Full Text PDF PubMed Scopus Google Scholar, J. Biol. 1998; PubMed Scopus Google Scholar). The is in collagen the of oxygen by the collagen is the of collagen in the oxygen J. J. PubMed Scopus Google Scholar). The of a function of Cygb with the that chondroblasts and osteoblasts show a high level of Cygb the chondrocytes and that collagen have levels of is also in with the that Cygb is enhanced in of the fibrotic liver (15Kawada N. Kristensen D.B. Asahina K. Nakatani K. Minamiyama Y. Seki S. Yoshizato K. J. Biol. Chem. 2001; 276: 25318-25323Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar). of also 2002; PubMed Scopus Google Scholar) and is by a in collagen J. Physiol. Physiol. 2000; PubMed Google Scholar, N. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar). be that the of collagen mRNA and protein is under in and in N. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, T. J. M.S. J. Physiol. 1993; PubMed Scopus Google Scholar, B. J. Physiol. Google Scholar, Y. S. Y. T. T. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. S. T. Y. Sci. 2002; PubMed Scopus Google Scholar). we have the expression of Cygb is enhanced under as is the level of Cygb oxygen conditions the oxygen of the collagen synthesis. to be is a of Cygb with the which in to the function of myoglobin, that Cygb facilitates the transport of O2 to the other of Cygb are A. M. A. S. Hankeln T. Burmester T. 2002; PubMed Scopus Google Scholar) and with the Cygb may the from or may that be by this Cygb may also be involved in a that the the of collagen J. Physiol. Physiol. 2000; PubMed Google Scholar, A. A. R. S. A. 1998; PubMed Scopus Google Scholar). Cygb is also found in some neurons of and the peripheral nervous but is that collagen is in these cells. In to the cell the neurons of both the cytoplasm and the a distinct function of Cygb in neuronal cells may be the Cygb may also O2 to the NO O2 the of NO from S. J. Biol. Chem. Full Text PDF PubMed Google Scholar). the other Cygb may be involved in a in the of Cygb the vertebrate globins (13Burmester T. Ebner B. Weich B. Hankeln T. Mol. Biol. Evol. 2002; 19: 416-421Crossref PubMed Scopus (436) Google Scholar), studies the function of this recently discovered heme but may also the that to respiratory and The Ebner the Northern and be to T. or T. B. in Nakatani et al. and K. also the presence of Cygb in the cell with