Hybrid proteins with neuregulin heparin-binding domain for targeting to heparan sulfate proteoglycans
Polypeptides of the neuregulin (NRG) heparin binding domain (N-HBD) and nucleic acids coding therefor are disclosed. In particular, fusion polypeptides are produced that comprise, as a targeting structure, a N-HBD polypeptide, fragment, homologue or functional derivative and a protein to be targeted. This is fused to a polypeptide or peptide being targeted (Ptrg) to cell surfaces rich in heparan sulfate proteoglycans to either activate or inhibit interactions at tyrosine kinase receptors. Such products are used to treat diseases or conditions where either agonism or antagonism at tyrosine kinase receptors has beneficial effects, including cancer and a multitude of diseases of the nervous system.
1. A fusion polypeptide comprising
(a) a first targeting polypeptide that binds heparan sulfate when said fusion polypeptide is permitted to contact cells or tissues, thereby localizing the fusion polypeptide to said heparan-sulfate rich cell or tissue surface;
wherein said fusion polypeptide binds to heparin or to a heparan sulfate proteoglycan when measured in a conventional heparin-binding or heparan-sulfate binding assay,
which first targeting polypeptide consists of:
(i) a human neuregulin heparin-binding domain (N-HBD) the sequence of which is SEQ ID NO:1; or
(ii) a heparin-binding fragment thereof the sequence of which is KWFKNGNELNRKNKPQNIKIQKKPGK (SEQ ID NO: 7); or
(iii) a heparin binding fragment the sequence of which is K-x-x-K-x-x-x-x-x-x-R-K-x-K-x-x-x-x-K-x-x-K-K-x-x-K (SEQ ID NO:10), wherein x is any amino acid; and
(b) a second targeted polypeptide P trg that is to be targeted and localized to the heparan sulfate-rich cell or tissue surface which second polypeptide is neuregulin (NRG), the extracellular domains of an erbB receptor, epidermal growth factor (EGF), a fibroblast growth factor (FGF), nerve growth factor (NGF) or a neurotrophic factor;
wherein said fusion polypeptide, through the action of said P trg , has enhanced biological activity in stimulating or blocking a target receptor compared to native P trg or P trg not fused to said first targeting polypeptide.
2. The fusion polypeptide of claim 1 wherein said first targeting polypeptide is fused directly to the second targeted polypeptide.
3. The fusion polypeptide of claim 1 wherein the first targeting polypeptide is said heparin binding fragment the sequence of which is SEQ ID NO: 7.
4. The fusion polypeptide of claim 1 wherein the first targeting polypeptide is said heparin-binding fragment the sequence of which is
K-x-x-K-x-x-x-x-x-x-R-K-x-K-x-x-x-K-x-x-K-K-x-x-K (SEQ ID NO:10), wherein x is any amino acid.
5. The fusion polypeptide of claim 1 that further comprises a linker peptide VPRGSD (SEQ ID NO:11) or DDKDWH (SEQ ID NO:12) between the first targeting polypeptide and the second targeted polypeptide.
6. A tandemly linked dimer or trimer of the fusion polypeptide of claim 1 .
7. The fusion polypeptide of claim 1 wherein said second targeted polypeptide P trg is an extracellular domain of an erbB receptor.
8. The fusion polypeptide of claim 1 wherein said second targeted polypeptide P trg is an epidermal growth factor or a neurotrophic factor.
9. The fusion polypeptide of claim 1 wherein said neurotrophic factor is neurotrophin, brain derived neurotrophic factor (BDNF), or glial derived neurotrophic factor (GDNF).
10. The fusion polypeptide of claim 1 wherein the first targeting polypeptide is said human N-HBD, the sequence of which is SEQ ID NO: 1.
11. A method for localizing a targeted polypeptide to a cell or tissue surface rich in heparan sulfate, and thereby enhancing the polypeptide's biological activity at said surface, comprising providing to said surface the fusion polypeptide of claim 1 , whereby the P trg of the fusion polypeptide is localized to said surface, such that the biological activity of the P trg is increased compared to the activity of (i) native P trg or (ii) P trg that is not fused to said targeting polypeptide.
12. The method of claim 11 wherein said providing is in vivo.