title: Androcam is a tissue-specific light chain for myosin VI in the Drosophila testis.
abstract: Myosin VI, a ubiquitously expressed unconventional myosin, has roles in a broad array of biological processes. Unusual for this motor family, myosin VI moves toward the minus (pointed) end of actin filaments. Myosin VI has two light chain binding sites that can both bind calmodulin (CaM). However unconventional myosins could use tissue-specific light chains to modify their activity. In the Drosophila testis, myosin VI is important for maintenance of moving actin structures, called actin cones, which mediate spermatid individualization. A CaM-related protein, Androcam (Acam), is abundantly expressed in the testis and like myosin VI, accumulates on these cones. We have investigated the possibility that Acam is a testis-specific light chain of Drosophila myosin VI. We find that Acam and myosin VI precisely colocalize at the leading edge of the actin cones and that myosin VI is necessary for this Acam localization. Further, myosin VI and Acam co-immunoprecipitate from the testis and interact in yeast two-hybrid assays. Finally Acam binds with high affinity to peptide versions of both myosin VI light chain binding sites. In contrast, although Drosophila CaM also shows high affinity interactions with these peptides, we cannot detect a CaM/myosin VI interaction in the testis. We conclude that Acam and not CaM acts as a myosin VI light chain in the Drosophila testis and hypothesize that it may alter the regulation of myosin VI in this tissue.
authors.affiliation: Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Frank
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Martin
authors.forename: Bridget N T
authors.initials: BN
authors.lastname: Gruender
authors.forename: Yung-Sheng R
authors.initials: YS
authors.lastname: Lee
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Simonette
authors.forename: Peter M
authors.initials: PM
authors.lastname: Bayley
authors.forename: Kathryn G
authors.initials: KG
authors.lastname: Miller
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Beckingham
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D008297:Male; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000378:metabolism*; D018994:Myosin Light Chains / Q000378:metabolism; D009928:Organ Specificity; D011485:Protein Binding; D016415:Sequence Alignment; D013737:Testis / Q000378:metabolism*
chemical_list: C090181:Acam protein, Drosophila; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D029721:Drosophila Proteins; D018994:Myosin Light Chains; C089785:myosin VI; D018995:Myosin Heavy Chains