title: Association of Lbc Rho guanine nucleotide exchange factor with alpha-catenin-related protein, alpha-catulin/CTNNAL1, supports serum response factor activation.
abstract: The Rho GTPase signaling pathway is required for actin cytoskeletal organization and serum response factor-dependent gene transcription. Lbc is a Rho-specific guanine nucleotide exchange factor that contains a modulatory C-terminal region. To elucidate Lbc regulatory mechanism(s), a yeast two-hybrid screen for proteins that interact with the Lbc C-terminal region was carried out, resulting in multiple isolation of cDNAs encoding the same 734-amino acid Lbc interacting protein. The Lbc interacting protein has homology with the alpha-catenin cell adhesion component and is identical to the alpha-catenin-like alpha-catulin protein of unknown function. The human alpha-catulin gene (CTNNAL1) maps to 9q31-32. Here we identify the predicted endogenous alpha-catulin product, document alpha-catulin and Lbc co-expression in multiple human cell lines, and show alpha-catulin and Lbc subcellular co-fractionation and intracellular localization. The required regions for Lbc and alpha-catulin interaction were mapped, and complex formation between Lbc and alpha-catulin in mammalian cells was detected. Functionally, alpha-catulin co-expression leads to increased Lbc-induced serum response factor activation in vivo as measured by a transcriptional reporter assay. Furthermore, alpha-catulin co-expression enhances Lbc-induced GTP-Rho formation in vivo. These results support the concept that the recently identified alpha-catulin protein may modulate Rho pathway signaling in vivo by providing a scaffold for the Lbc Rho guanine nucleotide exchange factor.
authors.affiliation: Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Park
authors.forename: Nhan T
authors.initials: NT
authors.lastname: Nguyen
authors.forename: Parmesh
authors.initials: P
authors.lastname: Dutt
authors.forename: Keith D
authors.initials: KD
authors.lastname: Merdek
authors.forename: Mariam
authors.initials: M
authors.lastname: Bashar
authors.forename: Paola
authors.initials: P
authors.lastname: Sterpetti
authors.forename: Alessandra
authors.initials: A
authors.lastname: Tosolini
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Testa
authors.forename: Deniz
authors.initials: D
authors.lastname: Toksoz
mesh_terms: D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D001665:Binding Sites; D002458:Cell Fractionation; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D027602:Serum Response Element; D026362:Serum Response Factor / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D051178:alpha Catenin
chemical_list: D054758:A Kinase Anchor Proteins; C085467:AKAP13 protein, human; D048868:Adaptor Proteins, Signal Transducing; C495273:CTNNA1 protein, human; C495274:CTNNAL1 protein, human; D003598:Cytoskeletal Proteins; D020662:Guanine Nucleotide Exchange Factors; D015778:Minor Histocompatibility Antigens; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D026362:Serum Response Factor; D051178:alpha Catenin