title: Single-molecule force spectroscopy of the Aplysia cell adhesion molecule reveals two homophilic bonds.
abstract: Aplysia californica neurons comprise a powerful model system for quantitative analysis of cellular and biophysical properties that are essential for neuronal development and function. The Aplysia cell adhesion molecule (apCAM), a member of the immunoglobulin superfamily of cell adhesion molecules, is present in the growth cone plasma membrane and involved in neurite growth, synapse formation, and synaptic plasticity. apCAM has been considered to be the Aplysia homolog of the vertebrate neural cell adhesion molecule (NCAM); however, whether apCAM exhibits similar binding properties and neuronal functions has not been fully established because of the lack of detailed binding data for the extracellular portion of apCAM. In this work, we used the atomic force microscope to perform single-molecule force spectroscopy of the extracellular region of apCAM and show for the first time (to our knowledge) that apCAM, like NCAM, is indeed a homophilic cell adhesion molecule. Furthermore, like NCAM, apCAM exhibits two distinct bonds in the trans configuration, although the kinetic and structural parameters of the apCAM bonds are quite different from those of NCAM. In summary, these single-molecule analyses further indicate that apCAM and NCAM are species homologs likely performing similar functions.
authors.affiliation: Nanomedicine Centre, School of Chemistry and Chemical Biology, University College Dublin, Dublin, Ireland.
authors.forename: E
authors.initials: E
authors.lastname: Martines
authors.forename: J
authors.initials: J
authors.lastname: Zhong
authors.forename: J
authors.initials: J
authors.lastname: Muzard
authors.forename: A C
authors.initials: AC
authors.lastname: Lee
authors.forename: B B
authors.initials: BB
authors.lastname: Akhremitchev
authors.forename: D M
authors.initials: DM
authors.lastname: Suter
authors.forename: G U
authors.initials: GU
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D015815:Cell Adhesion Molecules; D019006:Neural Cell Adhesion Molecules