Plasmin-mediated release of the guidance molecule F-spondin from the extracellular matrix.
Serine proteases are implicated in a variety of processes during neurogenesis, including cell migration, axon outgrowth, and synapse elimination. Tissue-type plasminogen activator and urokinase-type activator are expressed in the floor plate during embryonic development. F-spondin, a gene also expressed in the floor plate, encodes a secreted, extracellular matrix-attached protein that promotes outgrowth of commissural axons and inhibits outgrowth of motor axons. F-spondin is processed in vivo to yield an amino half protein that contains regions of homology to reelin and mindin, and a carboxyl half protein that contains either six or four thrombospondin type I repeats (TSRs). We have tested F-spondin to see whether it is subjected to processing by plasmin and to determine whether the processing modulates its biological activity. Plasmin cleaves F-spondin at its carboxyl terminus. By using nested deletion proteins and mutating potential plasmin cleavage sites, we have identified two cleavage sites, the first between the fifth and sixth TSRs, and the second at the fifth TSR. Analysis of the extracellular matrix (ECM) attachment properties of the TSRs revealed that the fifth and sixth TSRs bind to the ECM, but repeats 1-4 do not. Structural functional experiments revealed that two basic motives are required to elicit binding of TSR module to the ECM. We demonstrate further that plasmin releases the ECM-bound F-spondin protein.
Tzarfaty-Majar
V
V
Department of Anatomy and Cell Biology, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
López-Alemany
R
R
Feinstein
Y
Y
Gombau
L
L
Goldshmidt
O
O
Soriano
E
E
Muñoz-Cánoves
P
P
Klar
A
A
D000595:Amino Acid Sequence; D001665:Binding Sites; D002455:Cell Division; D002460:Cell Line; D002465:Cell Movement; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins; D005341:Fibrinolysin / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D017353:Gene Deletion; D006133:Growth Substances; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism*; D010455:Peptides; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D000091042:Reelin Protein; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D010959:Tissue Plasminogen Activator / Q000378:metabolism; D014162:Transfection
D016326:Extracellular Matrix Proteins; D006133:Growth Substances; D019006:Neural Cell Adhesion Molecules; D010455:Peptides; D000091042:Reelin Protein; C429104:SPON1 protein, human; D004247:DNA; C000717127:RELN protein, human; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin