as mentioned before , vegf - b is a pdgf / vegf family member that is completely devoid of any n - glycosylation . to analyze the effects of n - glycosylation on vegf - b , a n - glycosylation site was introduced into vegf - b . to determine the most appropriate site to introduce a mutation that would lead to n - glycosylation of vegf - b , the amino acid sequences of the first 99 amino acids of vegf - a , plgf and vegf - b , respectively , were aligned ( see fig1 ). the n - glycosylation sites of vegf - a and plgf at amino acids 65 - 67 are italicized in fig1 . nucleotides encoding a putative n - glycosylation site ( nxt ) were inserted at the position corresponding to nucleotides 286 - 294 of hvegf - b ( seq id no : 1 ). the replaced nucleotides normally found at positions 286 - 294 encode the amino acid residues qvr and these amino acid residues are bolded in fig1 . six mammalian expression vectors for both naturally occurring isoforms of vegf - b ( i . e ., vegf - b 167 and vegf - b 186 ) and for an artificial splice variant ( comprising exons 1 to 5 only ) were constructed with and without the putative n - glycosylation site . using pcr , nucleotides coding for a histidine tag were added to the c - terminal end of a nucleotide sequence coding for hvegf - b 186 . a nucleotide sequence coding for hvegf - b 186 - h 6 was then inserted into psectaga ( invitrogen , carlsbad , calif .) using standard cloning procedures to construct psectaga - hvegf - b 186 - h 6 . the full sequence of psectaga - hvegf - b 186 - h 6 is given in seq id no : 7 . to construct psectaga - hvegf - b 186 - h 6 - nxt , a pcr product of covering nucleotides 1 - 325 from genebank acc . no . u48801 was produced which introduced a n - glycosylation site at nucleotide positions 289 - 297 using the 3 ′ primer : 5 ′- tcggtaccggatcatgaggatctgcatggtgacgttgtgctgcccagtggcca - 3 ′ ( seq id no : 8 ). this pcr product was then cloned into a plasmid with full - length hvegf - b 186 where it used to replace the corresponding sequence to produce hvegf - b 186 - nxt . a histidine tag was then added by cloning together the n - terminal portion of hvegf - b 186 - nxt with the c - terminal portion of hvegf - b 186 - h 6 using standard cloning procedures to produce hvegf - b 186 - h 6 - nxt . the nucleotide sequence coding for hvegf - b 186 - h 6 - nxt was then inserted into psectaga ( invitrogen ) using standard cloning procedures to construct psectaga - hvegf - b 186 - h 6 - nxt . the full sequence of psectaga - hvegf - b 186 - h 6 - nxt is given in seq id no : 9 , and the plasmid is illustrated in fig2 . to construct psectaga - hvegf - b 167 - h 6 , a 349 bp pcr product was produced covering nucleotides 250 - 567 from genebank acc . no . u48801 , nucleotides coding for the histidine tag , a stop codon , the noti restriction site and terminal clamp nucleotides using the 5 ′ primer : 5 ′- cctgacgatggcctggagtgt - 3 ′ ( seq id no : 10 ) and the 3 ′ primer : 5 ′- gagcggccgctcaatgatgatgatgatgatgccttcgcagcttccggcac - 3 ′ ( seq id no : 11 ) and hvegf - b 167 as the template . the 349 bp pcr product was cut with kpni and noti and the kpni - noti fragment was inserted into psectaga - hvegf - b 186 - h 6 to replace the kpni - noti fragment removed from this vector using standard cloning procedures . the full sequence of psectaga - hvegf - b 167 - h 6 is given in seq id no : 12 . similarly , psectaga - hvegf - b 167 - h 6 - nxt was constructed as above except the kpni - noti fragment was inserted into psectaga - hvegf - b 186 - h 6 - nxt to replace the kpni - noti fragment removed from this vector . the full sequence of psectaga - hvegf - b 167 - h 6 - nxt is given in seq id no : 13 , and the plasmid is illustrated in fig3 . to construct psectaga - hvegf - b ex1 - 5 - h 6 , a 443 bp pcr product was obtained covering nucleotides 1 - 411 from genebank acc . no . u48801 , nucleotides coding for the histidine tag , a stop codon , the noti restriction site and terminal clamp nucleotides using the 5 ′ primer : 5 ′- caccatgagccctctgctcc - 3 ′ ( seq id no : 14 ) and 3 ′ primer : 5 - gagcggccgctcagtggtgatgatgatggtctggcttcacagcactg - 3 ′ ( seq id no : 15 ) and hvegf - b 167 as the template . the pcr product was cut with kpni and noti and the resulting 320 bp fragment was inserted into psectaga - hvegf - b 186 - h 6 - nxt to replace the kpni - noti removed from this vector using standard cloning procedures . the full sequence of psectaga - hvegf - b ex1 - 5 - h 6 is given in seq id no : 16 . to construct psectaga - hvegf - b ex1 - 5 - h 6 - nxt , the same procedures as above were used except the kpni - noti fragment was inserted into psectaga - hvegf - b 186 - h 6 - nxt to replace the kpni - noti fragment removed from this vector . the full sequence of psectaga - hvegf - b ex1 - 5 - h 6 - nxt is given in seq id no : 17 , and the plasmid is illustrated in fig4 . the following table d lists the expression vectors for the naturally occurring 186 and 167 amino acid isoforms of vegf - b and for the artificial splice variant ( comprising exon 1 to 5 only ), constructed with and without the potential glycosylation site ( nxt ). table d construct name protein psectaga - hvegf - b 186 - h 6 histidine - tagged vegf - b 186 psectaga - hvegf - b 186 - h 6 - nxt histidine - tagged and n - glycosylated vegf - b 186 psectaga - hvegf - b 167 - h 6 histidine - tagged vegf - b 167 psectaga - hvegf - b 167 - h 6 - nxt histidine - tagged and n - glycosylated vegf - b 167 psectaga - hvegf - b - exon1 - 5 - h 6 histidine - tagged vegf - b exons 1 to 5 only psectaga - hvegf - b - exon1 - 5 - h 6 - nxt histidine - tagged and n - glycosylated vegf - b exons 1 to 5 only the six mammalian expression vectors of human vegf - b described above along with expression vectors containing histidine - tagged vegf ( positive control ), a histidine - tagged vhd of vegf - c ( negative control ) and histidine - tagged hybrid 84 - 11 ( positive control ), respectively , were transfected into 293t cells using capo 4 - mediated transfection according to procedures described in sambrook , j . et al ., molecular cloning , a laboratory manual , ( cold spring harbor press , cold spring harbor , n . y . ), 16 . 33 - 16 . 36 ( 1989 ). 48 hours after transfection , the cells were metabolically labeled with s 35 methionine and s 35 cysteine ( promix , amersham ) for 12 to 24 hours . the conditioned supernatant was subjected to immunoprecipitation with an antiserum specific to human vegf - b ( 874 ) and a monoclonal antibody specific to pentahistidine ( h 5 mab , qiagen ). as seen in fig5 through 8 , the three constructs produced with the inserted putative n - glycosylation site are glycosylated . as can be seen from fig5 - 7 , comparison of supernatants and lysates and using heparin to release cell bound proteins shows that vegf - b 167 is almost completely retained at the cell surface or within the cell . about a 50 fold increase of vegf - b 167 can be detected in the supernatant upon glycosylation ( fig5 ). as shown in fig6 and 7 , vegf - b 167 is released into the supernatant by treatment with 100 μg / ml heparin two hours prior to harvest . it was also found that approximately two times more glycosylated vegf - b 167 can be detected in the supernatant of non - heparin treated 293t cells as compared to non - glycosylated vegf - b 167 treated with 200 μg / ml heparin for two hours prior to harvesting . in addition , there is about a three fold increase in the amount of the glycosylated vegf - b 167 detected in the supernatant by treatment with 200 μg / ml heparin two hours prior to harvest as compared to glycosylated vegf - b 167 without heparin treatment , and approximately a six fold increase in the amount of the glycosylated vegf - b 167 detected in the supernatant by treatment with 200 μg / ml heparin two hours prior to harvest as compared to the amount of non - glycosylated vegf - b 167 detected in the supernatant with the same heparin treatment . [ 0081 ] fig6 and 7 show that vegf - b 186 is also partially retained at the cell surface and within the cell . in contrast to vegf - b 167 , almost all of the vegf - b 186 is released into the supernatant upon glycosylation and heparin treatment ( fig6 and 7 ). there seems to be no significant difference in the amount of vegf - b 186 found in the supernatant between heparin - treated and untreated 293t cells . thus the difference of vegf - b 186 and n - glycosylated vegf - b 186 protein levels in the supernatant ( approximately three times more glycosylated vegf - b 186 ) seems to be mainly due to enhanced secretion and / or production and not due to the release of cell surface bound protein . [ 0082 ] fig8 shows that vegf - b exon1 - 5 is only efficiently released into the medium if it is n - glycosylated ( over a 50 fold increase in soluble protein ). this is unexpected since the signals retaining vegf - b at the cell surface are thought to reside in the exon 6 and 7 encoded domains ( fig8 ). treatment with heparin was not determined for this same reason . the ability of the recombinant vegf - b to bind vegf receptor 1 ( vegfr - 1 ) was analyzed using soluble fusion proteins consisting of the extracellular domain of vegfr - 1 and the fc portion of human igg1 ( vegfr - 1 - fc ). biosynthetically labeled conditioned medium derived from 293t cells transfected as above in example 3 were immunoprecipitated with protein a sepharose ( pas ) bound to the vegfr - 1 - ig . beads were washed three times with pbs , the bound protein eluted and resolved by reducing sds - page ( 15 %). the dried gels were exposed to phosphoimager plates for 12 - 24 hours . additionally , the cell lysates were immunoprecipitated with h 5 mab . when significant amounts of vegf - b were present in the supernatant , binding to vegfr - 1 could be observed . this was seen with vegf - b 186 - h 6 after treatment with 100 μg / ml heparin two hours prior to harvest , vegf - b 186 - nxt - h 6 and vegf - b exon 1 - 5 - nxt - h 6 ( fig7 and 8 ). the effects of introducing the n - glycosylation site into vegf - b can be assayed by measuring the ability of conditioned media from cells transfected with vegf - b167 and vegf - b167 - nxt and / or vegf - b186 and vegf - b186 - nxt to stimulate the survival of baf3 vegfr - 01ec / epor cells . for the assay , baf3 cells are used that are stably transfectd with a chimeric receptor consisting of the extracellular domain of vegf receptor 1 and the intracellular domain of the erythropoietin receptor . for survival , these cells need either interlukin - 3 or any growth factor capable of binding vegfr - 1 , e . g ., vegf - a , vegf - b or plgf . cells are plated to 96 - well plates at a density of 20 , 000 / well and grown in the presence of different amounts of medium conditioned by 293t cells that have been transfected with vegf - b167 and vegf - b167 - nxt , vegf - b186 and vegf - b186 - nxt , or both . conditioned medium from 293t cells transfected with a mock ( i . e ., empty ) vector may be used as a control . prior to the assay , the conditioned medium should be cleared from potentially interfering proteins by immunoprecipitation using appropriate antibodies . for example , vegf - a may be cleared from the conditioned medium prior to the assay using a mixture of monoclonal and polyclonal anti - hvegf antibodies , commercially available from r & amp ; d systems , minneapolis , minn . it is not necessary to preclear medium of plgf as the amounts expressed by cos cells ( if any ) are negligible and its effects are not visible in the baseline noise . after 48 hours , an mtt ( 3 -[ 4 , 5 - dimethylthiazol - 2 - yl ]- 2 , 5 - diphenyl - tetrazolium bromide thiazole blue ) colorimetric assay may be performed and data collected at 540 nm using a microtitreplate reader . to create the bglii site in the coding sequence of human vegfr - 1 just before the transmembrane domain , basepairs 1998 - 2268 of vegfr - 1 were pcr amplified with primers 5 ′- cctcagtgatcacacagtgg - 3 ′, containing the endogenous bcli site , and 5 ′- cagagatctattagacttgtcc - 3 ′, containing a bglii site , and the pcr fragment was cloned into the bcli - bglii sites of vegfr - 1 in pbluescript skii + ( stratagene ) vector . the transmembrane and intracellular domains of the human erythropoietin receptor were excised from epor × b + b / pcdnai and subcloned into the resulting plasmid as a bglii / noti fragment . the epor × b + b is a clone of epor which has an internal bglii site added at the putative transmembrane ( tm )/ extracellular ( ec ) domain junction for the in - frame ligation of rtk extracellular domains . the vector backbone is pcdna1 - amp (˜ 5 . 4 kb , the original 1 . 75 kb epor clone was subcloned into pcdna1 - amp using kpni , the sequence was reported by the lodish laboratory , mit ). an ˜ 1 kb fragment can be excised from this clone using bglii ( 5 ′)- noti ( 3 ′) digest which contains the tm and cytoplasmic domain of epor . the vegfr - 1 / epor construct was finally subcloned into the pef - bos vector ( mizushima et al ., nucleic acids research , 18 ( 17 ): 5322 sep . 11 , 1990 ) as a kpni / noti fragment . the resulting plasmid was electroporated into baf3 cells and stable cell pools were generated by selection with 250 micrograms / ml zoecin . the foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting . since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art , the invention should be construed broadly to include everything within the scope of the appended claims and equivalents thereof . atg agc cct ctg ctc cgc cgc ctg ctg ctc gcc gca ctc ctg cag ctg 48 gcc ccc gcc cag gcc cct gtc tcc cag cct gat gcc cct ggc cac cag 96 agg aaa gtg gtg tca tgg ata gat gtg tat act cgc gct acc tgc cag 144 arg lys val val ser trp ile asp val tyr thr arg ala thr cys gln ccc cgg gag gtg gtg gtg ccc ttg act gtg gag ctc atg ggc acc gtg 192 gcc aaa cag ctg gtg ccc agc tgc gtg act gtg cag cgc tgt ggt ggc 240 ala lys gln leu val pro ser cys val thr val gln arg cys gly gly tgc tgc cct gac gat ggc ctg gag tgt gtg ccc act ggg cag cac caa 288 gtc cgg atg cag atc ctc atg atc cgg tac ccg agc agt cag ctg ggg 336 gag atg tcc ctg gaa gaa cac agc cag tgt gaa tgc aga cct aaa aaa 384 aag gac agt gct gtg aag cca gac agc ccc agg ccc ctc tgc cca cgc 432 tgc acc cag cac cac cag cgc cct gac ccc cgg acc tgc cgc tgc cgc 480 tgc cga cgc cgc agc ttc ctc cgt tgc caa ggg cgg ggc tta gag ctc 528 aac cca gac acc tgc agg tgc cgg aag ctg cga agg tga 567 arg lys val val ser trp ile asp val tyr thr arg ala thr cys gln ala lys gln leu val pro ser cys val thr val gln arg cys gly gly atg agc cct ctg ctc cgc cgc ctg ctg ctc gcc gca ctc ctg cag ctg 48 gcc ccc gcc cag gcc cct gtc tcc cag cct gat gcc cct ggc cac cag 96 agg aaa gtg gtg tca tgg ata gat gtg tat act cgc gct acc tgc cag 144 arg lys val val ser trp ile asp val tyr thr arg ala thr cys gln ccc cgg gag gtg gtg gtg ccc ttg act gtg gag ctc atg ggc acc gtg 192 gcc aaa cag ctg gtg ccc agc tgc gtg act gtg cag cgc tgt ggt ggc 240 ala lys gln leu val pro ser cys val thr val gln arg cys gly gly tgc tgc cct gac gat ggc ctg gag tgt gtg ccc act ggg cag cac caa 288 gtc cgg atg cag atc ctc atg atc cgg tac ccg agc agt cag ctg ggg 336 gag atg tcc ctg gaa gaa cac agc cag tgt gaa tgc aga cct aaa aaa 384 aag gac agt gct gtg aag cca gac agg gct gcc act ccc cac cac cgt 432 ccc cag ccc cgt tct gtt ccg ggc tgg gac tct gcc ccc gga gca ccc 480 tcc cca gct gac atc acc cat ccc act cca gcc cca ggc ccc tct gcc 528 cac gct gca ccc agc acc acc agc gcc ctg acc ccc gga cct gcc gcc 576 gcc gct gcc gac gcc gca gct tcc tcc gtt gcc aag ggc ggg gct tag 624 arg lys val val ser trp ile asp val tyr thr arg ala thr cys gln ala lys gln leu val pro ser cys val thr val gln arg cys gly gly atg agc cct ctg ctc cgc cgc ctg ctg ctc gcc gca ctc ctg cag ctg 48 gcc ccc gcc cag gcc cct gtc tcc cag cct gat gcc cct ggc cac cag 96 agg aaa gtg gtg tca tgg ata gat gtg tat act cgc gct acc tgc cag 144 arg lys val val ser trp ile asp val tyr thr arg ala thr cys gln ccc cgg gag gtg gtg gtg ccc ttg act gtg gag ctc atg ggc acc gtg 192 gcc aaa cag ctg gtg ccc agc tgc gtg act gtg cag cgc tgt ggt ggc 240 ala lys gln leu val pro ser cys val thr val gln arg cys gly gly tgc tgc cct gac gat ggc ctg gag tgt gtg ccc act ggg cag cac caa 288 gtc cgg atg cag atc ctc atg atc cgg tac ccg agc agt cag ctg ggg 336 gag atg tcc ctg gaa gaa cac agc cag tgt gaa tgc aga cct aaa aaa 384 arg lys val val ser trp ile asp val tyr thr arg ala thr cys gln ala lys gln leu val pro ser cys val thr val gln arg cys gly gly
n - glycosylated vegf - b proteins , nucleic molecule encoding these proteins , pharmaceutical compositions containing them and a method for increasing the amount of a soluble vegf - b protein . the vegf - b proteins are useful in stimulating and maintaining angiogenesis .