Microtubule Actin Cross-Linking Factor (MACF): A Hybrid of Dystonin and Dystrophin That Can Interact with the Actin and Microtubule Cytoskeletons

• Published in: The Journal of cell biology 1999-12, Vol.147 (6), p.1275-1285
• Main Authors: Leung, Conrad L., Sun, Dongming, Zheng, Min, Knowles, David R., Ronald K. H. Liem
• Format: Article
• Language: English
• Subjects: Actin Cytoskeleton - metabolism; Actins; Actins - metabolism; Amino Acid Motifs; Amino Acid Sequence; Animals; Antibodies; BPAG1-n protein; Carrier Proteins; Cellular biology; Cloning; Cloning, Molecular; Complementary DNA; COS Cells; Cytoskeletal Proteins - chemistry; Cytoskeleton; Cytoskeleton - metabolism; Deoxyribonucleic acid; DNA; Drosophila Proteins; Dystonin; Dystrophin - chemistry; Embryo, Mammalian - metabolism; Gas2 protein; Humans; Kakapo protein; Mice; Microfilament Proteins - chemistry; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Microfilaments; Microtubule actin cross-linking factor; Microtubules; Microtubules - metabolism; Molecular Sequence Data; Mutation; Nerve Tissue Proteins - chemistry; Neurons; Original; Plakins; Protein Binding; Protein Structure, Secondary; Proteins; Recombinant Fusion Proteins - metabolism; RNA, Messenger - analysis; RNA, Messenger - genetics; Rodents; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Stress fibers
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.147.6.1275

We cloned and characterized a full-length cDNA of mouse actin cross-linking family 7 (mACF7) by sequential rapid amplification of cDNA ends-PCR. The completed mACF7 cDNA is 17 kb and codes for a 608-kD protein. The closest relative of mACF7 is the Drosophila protein Kakapo, which shares similar architecture with mACF7. mACF7 contains a putative actin-binding domain and a plakin-like domain that are highly homologous to dystonin (BPAG1-n) at its NH2terminus. However, unlike dystonin, mACF7 does not contain a coiled-coil rod domain; instead, the rod domain of mACF7 is made up of 23 dystrophin-like spectrin repeats. At its COOH terminus, mACF7 contains two putative EF-hand calcium-binding motifs and a segment homologous to the growth arrest-specific protein, Gas2. In this paper, we demonstrate that the NH2-terminal actin-binding domain of mACF7 is functional both in vivo and in vitro. More importantly, we found that the COOH-terminal domain of mACF7 interacts with and stabilizes microtubules. In transfected cells full-length mACF7 can associate not only with actin but also with microtubules. Hence, we suggest a modified name: MACF (microtubule actin cross-linking factor). The properties of MACF are consistent with the observation that mutations in kakapo cause disorganization of microtubules in epidermal muscle attachment cells and some sensory neurons.