title: Identification of a high-affinity network of secretagogin-binding proteins involved in vesicle secretion.
abstract: Secretagogin is a hexa EF-hand Ca(2+)-binding protein expressed in neuroendocrine, pancreatic endocrine and retinal cells. The protein has been noted for its expression in specific neuronal subtypes in the support of hierarchical organizing principles in the mammalian brain. Secretagogin has previously been found to interact with SNAP25 involved in Ca(2+)-induced exocytosis. Here, the cellular interaction network of secretagogin has been expanded with nine proteins: SNAP-23, DOC2alpha, ARFGAP2, rootletin, KIF5B, β-tubulin, DDAH-2, ATP-synthase and myeloid leukemia factor 2, based on screening of a high content protein array and validation and quantification of binding with surface plasmon resonance and GST pulldown assays. All targets have association rate constants in the range 10(4)-10(6) M(-1) s(-1), dissociation rate constants in the range 10(-3)-10(-5) s(-1) and equilibrium dissociation constants in the 100 pM to 10 nM range. The novel target SNAP23 is an essential component of the high affinity receptor for the general membrane fusion machinery and an important regulator of transport vesicle docking and fusion. Complementary roles in vesicle trafficking are known for ARFGAP2 and DOC2alpha in regulating fusion of vesicles to membranes, kinesin 5B and tubulin for transport of vesicles in the cell, while rootletin builds up the rootlet believed to function as a scaffold for vesicles. The identification of a discrete network of interacting proteins that mediate secretion and vesicle trafficking suggests a regulatory role for secretagogin in these processes.
authors.affiliation: Departments of Biophysical Chemistry and Biochemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: Mikael C
authors.initials: MC
authors.lastname: Bauer
authors.forename: David J
authors.initials: DJ
authors.lastname: O'Connell
authors.forename: Magdalena
authors.initials: M
authors.lastname: Maj
authors.forename: Ludwig
authors.initials: L
authors.lastname: Wagner
authors.forename: Dolores J
authors.initials: DJ
authors.lastname: Cahill
authors.forename: Sara
authors.initials: S
authors.lastname: Linse
mesh_terms: D002135:Calcium-Binding Proteins / Q000378:metabolism*; D020832:EF Hand Motifs; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D040081:Protein Array Analysis; D011485:Protein Binding; D015203:Reproducibility of Results; D022142:Secretory Vesicles / Q000378:metabolism*; D020349:Surface Plasmon Resonance
chemical_list: D002135:Calcium-Binding Proteins