Actin polymerization is stimulated by actin cross-linking protein palladin

Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G.; Orlova, Albina; Beck, Moriah R.

doi:10.1042/bj20151050

Cited by 25 publications

(59 citation statements)

References 69 publications

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“…3d). Moreover, chelation of calcium from the G-actin did not alter the actin nucleation and polymerization activity of palladin, which is in agreement with the mechanism proposed by Gurung et al (2016), whereby the binding of Palld-Ig3 to actin transforms G-actin to nucleation- and polymerization-competent form through charge neutralization or conformational change [34]. …”

Section: Resultssupporting

confidence: 87%

“…Therefore, we next investigated the effect of PI(4,5)P 2 on the actin crosslinking activity of Palld-Ig3. We chose non-polymerizing conditions because the actin crosslinkng activity of Palld-Ig3 is significantly higher as a result of co-polymerization with actin, as opposed to the addition of Palld-Ig3 to pre-polymerized actin filaments [34]. We observed a significant decrease in actin crosslinking [15–40% with PI(4,5)P 2 as opposed to 60% without PI(4,5)P 2 ] in a dose-dependent manner upon the addition of varying concentrations of PI(4,5)P 2 mixed with Palld-Ig3 and globular or monomeric actin (G-actin) (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, we have shown that the Palld-Ig3 domain also promotes de novo actin nucleation and polymerization [34]. Therefore, we next sought to determine whether PI(4,5)P 2 binding has any effect on palladin’s actin nucleation and polymerization activity.…”

Section: Resultsmentioning

confidence: 99%

“…The largest isoform of palladin (isoform #1, ~200 kDa) contains five immunoglobulin (Ig) domains: two amino terminal Ig domains (Ig1, Ig2), followed by two polyproline-rich regions and three C-terminal Ig domains (Ig3–Ig5) [32,33]. The Ig domain 3 of palladin (Palld-Ig3) has been shown to be both necessary and sufficient for both actin binding and crosslinking [25,26,34]. Despite the fact that the Ig4 domain and the linker between the Ig3 and Ig4 domains of palladin do not interact directly with actin, their addition increases actin binding and crosslinking activity significantly over that of the Ig3 domain alone [35].…”

Section: Introductionmentioning

confidence: 99%

“…Our lab has recently shown that palladin can increase the rate of actin polymerization and also alters the organization of the resulting filaments [34]. Moreover, removal of the actin binding domain (Palld-Ig3) results in the relocation of palladin to the nucleus [26], suggesting that direct binding with actin has major implications for palladin’s role in cytoskeletal reorganization.…”

Section: Introductionmentioning

confidence: 99%

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Phosphoinositide Binding Inhibits Actin Crosslinking and Polymerization by Palladin

Yadav

Vattepu

Beck

2016

Journal of Molecular Biology

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Actin cytoskeleton remodeling requires the coordinated action of a large number of actin binding proteins that reorganize the actin cytoskeleton by promoting polymerization, stabilizing filaments, causing branching, or crosslinking filaments. Palladin is a key cytoskeletal actin binding protein whose normal function is to enable cell motility during development of tissues and organs of the embryo and in wound healing, but palladin is also responsible for regulating the ability of cancer cells to become invasive and metastatic. The membrane phosphoinositide phosphatidylinositol (PI) 4,5-bisphosphate [PI(4,5)P2] is a well-known precursor for intracellular signaling and a bona fide regulator of actin cytoskeleton reorganization. Our results show that two palladin domains [immunoglobulin (Ig) 3 and 34] interact with the head group of PI(4,5)P2 with moderate affinity (apparent Kd = 17 μM). Interactions with PI(4,5)P2 decrease the actin polymerizing activity of Ig domain 3 of palladin (Palld-Ig3). Furthermore, NMR titration and docking studies show that residues K38 and K51, which are present on the β-sheet C and D, form salt bridges with the head group of PI(4,5)P2. Moreover, charge neutralization at lysine 38 in the Palld-Ig3 domain severely limits the actin polymerizing and bundling activity of Palld-Ig3. Our results provide biochemical proof that PI(4,5)P2 functions as a moderator of palladin activity and have also identified residues directly involved in the crosslinking activity of palladin.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phosphoinositide Binding Inhibits Actin Crosslinking and Polymerization by Palladin

Yadav

Vattepu

Beck

2016

Journal of Molecular Biology

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Glypican‐4 regulated actin cytoskeletal reorganization in glucocorticoid treated trabecular meshwork cells and involvement of Wnt/PCP signaling

Maddala

Eldawy

Bachman

et al. 2023

Journal Cellular Physiology

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A common adverse response to the clinical use of glucocorticoids (GCs) is elevated intraocular pressure (IOP) which is a major risk factor for glaucoma. Elevated IOP arises due to impaired outflow of aqueous humor (AH) through the trabecular meshwork (TM). Although GC‐induced changes in actin cytoskeletal dynamics, contractile characteristics, and cell adhesive interactions of TM cells are believed to influence AH outflow and IOP, the molecular mechanisms mediating changes in these cellular characteristics are poorly understood. Our studies focused on evaluating changes in the cytoskeletal and cytoskeletal‐associated protein (cytoskeletome) profile of human TM cells treated with dexamethasone (Dex) using label‐free mass spectrometric quantification, identified elevated levels of specific proteins known to regulate actin stress fiber formation, contraction, actin networks crosslinking, cell adhesion, and Wnt signaling, including LIMCH1, ArgBP2, CNN3, ITGBL1, CTGF, palladin, FAT1, DIAPH2, EPHA4, SIPA1L1, and GPC4. Several of these proteins colocalized with the actin cytoskeleton and underwent alterations in distribution profile in TM cells treated with Dex, and an inhibitor of Abl/Src kinases. Wnt/Planar Cell Polarity (PCP) signaling agonists‐Wnt5a and 5b were detected prominently in the cytoskeletome fraction of TM cells, and studies using siRNA to suppress expression of glypican‐4 (GPC4), a known modulator of the Wnt/PCP pathway revealed that GPC4 deficiency impairs Dex induced actin stress fiber formation, and activation of c‐Jun N‐terminal Kinase (JNK) and Rho kinase. Additionally, while Dex augmented, GPC4 deficiency suppressed the formation of actin stress fibers in TM cells in the presence of Dex and Wnt5a. Taken together, these results identify the GPC4‐dependent Wnt/PCP signaling pathway as one of the crucial upstream regulators of Dex induced actin cytoskeletal reorganization and cell adhesion in TM cells, opening an opportunity to target the GPC4/Wnt/PCP pathway for treatment of ocular hypertension in glaucoma.

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Myopalladin promotes muscle growth through modulation of the serum response factor pathway

Filomena

Yamamoto

Caremani

et al. 2019

J cachexia sarcopenia muscle

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Background Myopalladin (MYPN) is a striated muscle‐specific, immunoglobulin‐containing protein located in the Z‐line and I‐band of the sarcomere as well as the nucleus. Heterozygous MYPN gene mutations are associated with hypertrophic, dilated, and restrictive cardiomyopathy, and homozygous loss‐of‐function truncating mutations have recently been identified in patients with cap myopathy, nemaline myopathy, and congenital myopathy with hanging big toe. Methods Constitutive MYPN knockout (MKO) mice were generated, and the role of MYPN in skeletal muscle was studied through molecular, cellular, biochemical, structural, biomechanical, and physiological studies in vivo and in vitro. Results MKO mice were 13% smaller compared with wild‐type controls and exhibited a 48% reduction in myofibre cross‐sectional area (CSA) and significantly increased fibre number. Similarly, reduced myotube width was observed in MKO primary myoblast cultures. Biomechanical studies showed reduced isometric force and power output in MKO mice as a result of the reduced CSA, whereas the force developed by each myosin molecular motor was unaffected. While the performance by treadmill running was similar in MKO and wild‐type mice, MKO mice showed progressively decreased exercise capability, Z‐line damage, and signs of muscle regeneration following consecutive days of downhill running. Additionally, MKO muscle exhibited progressive Z‐line widening starting from 8 months of age. RNA‐sequencing analysis revealed down‐regulation of serum response factor (SRF)‐target genes in muscles from postnatal MKO mice, important for muscle growth and differentiation. The SRF pathway is regulated by actin dynamics as binding of globular actin to the SRF‐cofactor myocardin‐related transcription factor A (MRTF‐A) prevents its translocation to the nucleus where it binds and activates SRF. MYPN was found to bind and bundle filamentous actin as well as interact with MRTF‐A. In particular, while MYPN reduced actin polymerization, it strongly inhibited actin depolymerization and consequently increased MRTF‐A‐mediated activation of SRF signalling in myogenic cells. Reduced myotube width in MKO primary myoblast cultures was rescued by transduction with constitutive active SRF, demonstrating that MYPN promotes skeletal muscle growth through activation of the SRF pathway. Conclusions Myopalladin plays a critical role in the control of skeletal muscle growth through its effect on actin dynamics and consequently the SRF pathway. In addition, MYPN is important for the maintenance of Z‐line integrity during exercise and aging. These results suggest that muscle weakness in patients with biallelic MYPN mutations may be associated with reduced myofibre CSA and SRF signalling and that the disease phenotype may be aggravated by exercise.

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Actin polymerization is stimulated by actin cross-linking protein palladin

Cited by 25 publications

References 69 publications

Phosphoinositide Binding Inhibits Actin Crosslinking and Polymerization by Palladin

Phosphoinositide Binding Inhibits Actin Crosslinking and Polymerization by Palladin

Glypican‐4 regulated actin cytoskeletal reorganization in glucocorticoid treated trabecular meshwork cells and involvement of Wnt/PCP signaling

Myopalladin promotes muscle growth through modulation of the serum response factor pathway

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