Abstract
Utrophin is a component of the platelet membrane cytoskeleton and participates in cytoskeletal reorganization (Earnest, J. P., Santos, G. F., Zuerbig, S., and Fox, J. E. B. (1995) J. Biol. Chem. 270, 27259-27265). Although platelets do not contain dystrophin, the identification of smaller C-terminal isoforms of dystrophin, including Dp71, which are expressed in a wide range of nonmuscle tissues and cell lines, has not been investigated. In this report, we have identified Dp71 protein variants of 55-60 kDa (designated Dp71Delta(110)) in the membrane cytoskeleton of human platelets. Both Dp71Delta(110) and utrophin sediment from lysed platelets along with the high speed detergent-insoluble pellet, which contains components of the membrane cytoskeleton. Like the membrane cytoskeletal proteins vinculin and spectrin, Dp71Delta(110) and utrophin redistributed from the high speed detergent-insoluble pellet to the integrin-rich low speed pellet of thrombin-stimulated platelets. Immunoelectron microscopy provided further evidence that Dp71Delta(110) was localized to the submembranous cytoskeleton. In addition to Dp71Delta(110), platelets contained several components of the dystrophin-associated protein complex, including beta-dystroglycan and syntrophin. To better understand the potential function of Dp71Delta(110), collagen adhesion assays were performed on platelets isolated from wild-type or Dp71-deficient (mdx(3cv)) mice. Adhesion to collagen in response to thrombin was significantly decreased in platelets isolated from mdx(3cv) mice, compared with wild-type platelets. Collectively, our results provide evidence that Dp71Delta(110) is a component of the platelet membrane cytoskeleton, is involved in cytoskeletal reorganization and/or signaling, and plays a role in thrombin-mediated platelet adhesion.
Highlights
Utrophin is a component of the platelet membrane cytoskeleton and participates in cytoskeletal reorganization
Because Dp71 transcripts are alternatively spliced for exons 71 and/or 78 in a wide range of nonmuscle tissues, multiple Dp71 protein products of 70 –75 kDa are generated, all of which can be identified using dystrophin-specific antibodies directed against the C terminus of the protein [8]
In addition to these Dp71 isoforms, we have recently identified a subpopulation of Dp71 transcripts in human brain that do not contain exons 71–74 and are alternatively spliced for exon 78 [14]
Summary
Utrophin is a component of the platelet membrane cytoskeleton and participates in cytoskeletal reorganization Because Dp71 transcripts are alternatively spliced for exons 71 and/or 78 in a wide range of nonmuscle tissues, multiple Dp71 protein products of 70 –75 kDa are generated, all of which can be identified using dystrophin-specific antibodies directed against the C terminus of the protein [8]. In addition to these Dp71 isoforms, we have recently identified a subpopulation of Dp71 transcripts in human brain that do not contain exons 71–74 and are alternatively spliced for exon 78 [14]. DAPC, dystrophin-associated protein complex; Dp71⌬110, 55- to 60-kDa variant of Dp71; Dp71⌬110m, Dp71⌬110 containing the C-terminal sequences of muscle dystrophin; Dp71⌬110a, Dp71⌬110 containing the alternative 31-amino acid C-terminal sequence due to the splicing of exon 78; PBS, phosphate-buffered saline; HRP, horseradish peroxidase; BSA, bovine serum albumin; RFU, relative fluorescence units
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
