title: Merlin links to the cAMP neuronal signaling pathway by anchoring the RIbeta subunit of protein kinase A.
abstract: The cAMP-protein kinase A (PKA) pathway, important in neuronal signaling, is regulated by molecules that bind and target PKA regulatory subunits. Of four regulatory subunits, RIbeta is most abundantly expressed in brain. The RIbeta knockout mouse has defects in hippocampal synaptic plasticity, suggesting a role for RIbeta in learning and memory-related functions. Molecules that interact with or regulate RIbeta are still unknown. We identified the neurofibromatosis 2 tumor suppressor protein merlin (schwannomin), a molecule related to the ezrin-radixin-moesin family of membrane-cytoskeleton linker proteins, as a binding partner for RIbeta. Merlin and RIbeta demonstrated a similar expression pattern in central nervous system neurons and an overlapping subcellular localization in cultured hippocampal neurons and transfected cells. The proteins were coprecipitated from brain lysates by cAMP-agarose and coimmunoprecipited from cellular lysates with specific antibodies. In vitro binding studies verified that the interaction is direct. The interaction appeared to be under conformational regulation and was mediated via the alpha-helical region of merlin. Sequence comparison between merlin and known PKA anchoring proteins identified a conserved alpha-helical PKA anchoring protein motif in merlin. These results identify merlin as the first neuronal binding partner for PKA-RIbeta and suggest a novel function for merlin in connecting neuronal cytoskeleton to PKA signaling.
authors.affiliation: Biomedicum Helsinki, Department of Pathology, Neuroscience Center, Institute of Biotechnology, University of Helsinki and Helsinki University Central Hospital, 00014 Helsinki, Finland. mikaela.gronholm@helsinki.fi
authors.forename: Mikaela
authors.initials: M
authors.lastname: Grönholm
authors.forename: Lutz
authors.initials: L
authors.lastname: Vossebein
authors.forename: Cathrine R
authors.initials: CR
authors.lastname: Carlson
authors.forename: Juha
authors.initials: J
authors.lastname: Kuja-Panula
authors.forename: Tambet
authors.initials: T
authors.lastname: Teesalu
authors.forename: Kaija
authors.initials: K
authors.lastname: Alfthan
authors.forename: Antti
authors.initials: A
authors.lastname: Vaheri
authors.forename: Heikki
authors.initials: H
authors.lastname: Rauvala
authors.forename: Friedrich W
authors.initials: FW
authors.lastname: Herberg
authors.forename: Kjetil
authors.initials: K
authors.lastname: Taskén
authors.forename: Olli
authors.initials: O
authors.lastname: Carpén
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008969:Molecular Sequence Data; D025581:Neurofibromin 2 / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry; D011233:Precipitin Tests; D011485:Protein Binding; D051381:Rats; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014162:Transfection; D020798:Two-Hybrid System Techniques; D000099149:Ezrin
chemical_list: D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D003598:Cytoskeletal Proteins; D025581:Neurofibromin 2; D010455:Peptides; D010750:Phosphoproteins; D000099149:Ezrin