Identification of M-CSF agonists and antagonists

A method for identifying candidate human macrophage-colony stimulating factor (M-CSF) agonists or antagonists, the method comprising the steps of:

• a) crystallizing an M-CSF dimer to form at least one M-CSF crystal, the dimer composed of two M-CSF monomers which may be the same or different, at least one of said monomers having at least one but less than five amino acid substitutions, the substitutions and residue positions selected from the group consisting of His15.fwdarw.Ala or Leu, Gln17.fwdarw.Ala or Glu, Gln79.fwdarw.Ala or Asp, Arg86.fwdarw.Glu or Asp, Glu115.fwdarw.Ala, Glu41.fwdarw.Lys or Arg, Lys93.fwdarw.Ala or Glu, Asp99.fwdarw.Lys or Arg, Leu55.fwdarw.Gln or Asn, Ser18.fwdarw.Ala or Lys, Gln20.fwdarw.Ala or Asp, Arg21.fwdarw.Ala or Glu, Ile75.fwdarw.Lys or Glu, Val78.fwdarw.Lys or Arg, Leu85.fwdarw.Glu or Asn, Asp69.fwdarw.Lys or Arg, Asn70.fwdarw.Ala or Glu, His9.fwdarw.Ala or Asp, Asn63.fwdarw.Lys or Arg, Thr34.fwdarw.Gln or Lys, Cys157.fwdarw.Ser, and Cys159.fwdarw.Ser, one or more of said monomers being a full length mature human M-CSF, or being an N.DELTA.3 deletion mutein, or having a carboxy truncation ending at a residue position selected from the group consisting of 158 and 221, or a combination thereof, all said residue positions being relative to mature human M-CSF;
• b) irradiating the M-CSF crystal produced by the procedure of step (a) to obtain a diffraction pattern of the M-CSF crystal;
• c) determining the three-dimensional structure of M-CSF from the diffraction pattern, the three-dimensional structure including an M-CSF receptor-binding region;
• and
• d) identifying a candidate human M-CSF agonist or antagonist having a three-dimensional structure of the M-CSF binding region, wherein said candidate M-CSF agonist or antagonist has an altered signal transduction capacity relative to mature human M-CSF on M-CSF responsive cells.