Methods for identifying inhibitors of mannan-binding lectin associated serine protease (MASP) proteins and uses thereof

1. A method of screening for one or more small molecules capable of inhibiting MBL-associated serine protease (MASP) protein activity, the method comprising:

(a) contacting a MASP protein, or a portion thereof comprising a CUB1 or a CUB2 domain, with at least one or more small molecule(s) in the presence of a polypeptide comprising at least one collagen-like binding domain of a mannose-binding lectin (MBL) or ficolin, and Ca 2+ , wherein the collagen-like binding domain comprises one or more of the amino acid sequence OGKXGP (SEQ ID NO:3), wherein O is hydroxyproline and X is an aliphatic amino acid residue or methionine residue;

(b) performing an assay to determine the affinity of Ca 2+ -dependent binding between the MASP protein, or portion thereof comprising a CUB1 or a CUB2 domain, and the polypeptide comprising the at least one collagen-like binding domain comprising one or more of the amino acid sequence OGKXGP (SEQ ID NO:3), wherein O is hydroxyproline and X is an aliphatic amino acid residue or methionine residue, identifying small molecule(s) that reduce the affinity of Ca 2+ -dependent binding between the MASP protein or the portion thereof comprising a CUB1 or a CUB2 domain and the polypeptide comprising the collagen-like binding domain of MBL or ficolin; and

(c) determining the level of MASP protein activity in the presence and absence of the small molecule(s) identified in accordance with step (b);

wherein reduced MASP protein activity determined in the presence of the small molecule in step (c) compared to the level of MASP protein activity determined in the absence of the small molecule indicates the capacity of the small molecule to inhibit MASP protein activity.

2. The method of claim 1 , wherein the level of MASP protein activity is determined by performing an assay to determine the ability of the MASP protein to activate the lectin or classical complement pathway.

3. The method of claim 1 , wherein the method comprises the use of a full length MASP protein, and the level of MASP protein activity is determined by performing an assay to determine the ability of the MASP protein to activate complement.

4. The method of claim 1 , wherein the assay according to step (b) is determined using surface plasmon resonance.

5. The method of claim 1 , wherein the MASP protein is a member of the group consisting of MASP-1 protein, MASP-2 protein, and a MASP-3 protein.

6. The method of claim 1 , wherein the one or more small molecules is a small amine.

7. The method of claim 1 , wherein one or more small molecules is a member selected from the group consisting of methylamine, ethylamine, lysine, dGMP-Deoxyguanosine monophosphate, dCMP-Deoxycytidine monophosphate, dAMP-Deoxyadenosine monophosphate, dTMP-Thymidine 5′-monophosphate, GMP-Guanosine monophosphate, AMP-Adenosine monophosphate, TMP-Thiamine monophosphate, UMP-Uridine monophosphate, dGTP-Deoxyguanosine triphosphate, dCTP-Deoxycytidine triphosphate, dATP-deoxyadenosine triphosphate, dTTP-Thymidine triphosphate, GTP Guanosine triphosphate, CTP-Cytidine triphosphate, ATP-Adenosine Triphosphate, TTP-Thymidine triphosphate, and UTP-Uridine triphosphate.

8. The method of claim 1 , wherein the one or more small molecules comprises an NH 3 group.

9. The method of claim 1 , wherein the one or more small molecules have molecular weight(s) of less than 1,000 daltons.

10. The method of claim 1 , wherein the small molecule with an indicated capacity to inhibit MASP protein activity disrupts the binding between at least one of residues Glu216, His218, Lys225, Asp263, and Ser265 of the MASP protein, with reference to SEQ ID NO: 6, and MBL or ficolin.