Multi-Tasking Role of the Mechanosensing Protein Ankrd2 in the Signaling Network of Striated Muscle

Abstract

BackgroundAnkrd2 (also known as Arpp) together with Ankrd1/CARP and DARP are members of the MARP mechanosensing proteins that form a complex with titin (N2A)/calpain 3 protease/myopalladin. In muscle, Ankrd2 is located in the I-band of the sarcomere and moves to the nucleus of adjacent myofibers on muscle injury. In myoblasts it is predominantly in the nucleus and on differentiation shifts from the nucleus to the cytoplasm. In agreement with its role as a sensor it interacts both with sarcomeric proteins and transcription factors.Methodology/Principal FindingsExpression profiling of endogenous Ankrd2 silenced in human myotubes was undertaken to elucidate its role as an intermediary in cell signaling pathways. Silencing Ankrd2 expression altered the expression of genes involved in both intercellular communication (cytokine-cytokine receptor interaction, endocytosis, focal adhesion, tight junction, gap junction and regulation of the actin cytoskeleton) and intracellular communication (calcium, insulin, MAPK, p53, TGF-β and Wnt signaling). The significance of Ankrd2 in cell signaling was strengthened by the fact that we were able to show for the first time that Nkx2.5 and p53 are upstream effectors of the Ankrd2 gene and that Ankrd1/CARP, another MARP member, can modulate the transcriptional ability of MyoD on the Ankrd2 promoter. Another novel finding was the interaction between Ankrd2 and proteins with PDZ and SH3 domains, further supporting its role in signaling. It is noteworthy that we demonstrated that transcription factors PAX6, LHX2, NFIL3 and MECP2, were able to bind both the Ankrd2 protein and its promoter indicating the presence of a regulatory feedback loop mechanism.Conclusions/SignificanceIn conclusion we demonstrate that Ankrd2 is a potent regulator in muscle cells affecting a multitude of pathways and processes.

Global Deletion of Ankrd1 Results in a Wound-Healing Phenotype Associated with Dermal Fibroblast Dysfunction

“…Indeed, there appeared to be a reduced level of Ankrd2 expression that could be related to the inhibition of MyoD-dependent Ankrd2 expression after knockdown of Ankrd1 by siRNA treatment of skeletal muscle. 16 Deletion of all three MARPs provides evidence of skeletal muscle weakness, 6 but the mouse strains in that study showed no developmental abnormalities, as in this report, or, in a more recent report, response to cardiac pressure overload. 7 …”

“…This response was consistent with evidence for an involvement of ANKRD1 in MyoD Q37 -dependent transcription of Ankrd2. 16 In summary, these data showed that neither Ankrd2 nor Ankrd23 compensated, at the transcriptional level, for the loss of Ankrd1.…”

“…16 On the basis of preliminary observations in 18-hour wounds (Supplemental Figure S3), we analyzed wound contraction in FLOX and KO mice to the point of near closure. Bilateral, full-thickness, unsplinted excisional wounds (6 mm thick) were made on the dorsum and imaged daily for 8 days (Figure 3 ½F3 ½F3 A).…”

Label-free Quantitative Protein Profiling of vastus lateralis Muscle During Human Aging

“…Myofibrillar Proteins-Ankyrin repeat domain-containing protein 2 is localized in both the nucleus and the sarcomeric I-band, and is involved in a mechano-signaling pathway that links myofibrillar stress to gene expression (34). It is preferentially expressed in slow type I fibers of human muscle (35), and its up-regulation is in agreement with a fast-to-slow transition during aging.…”

Emery-Dreifuss Muscular Dystrophy-Associated Mutant Forms of Lamin A Recruit the Stress Responsive Protein Ankrd2 into the Nucleus, Affecting the Cellular Response to Oxidative Stress

“…In the nucleus, Ankrd2 binds to multiple transcription factors, such as YB1, ID3, PAX6, LHX2 and MECP2 [6-8], as well as p53, and PML [6]. In the cytoplasm, Ankrd2 interacts with proteins involved in cell signaling, such as Akt2 [9], and PLCγ [7], but also with sarcomeric proteins, such as telethonin [6], titin [10] and ZASP6 [11]. …”