Pak2 restrains endomitosis during megakaryopoiesis and alters cytoskeleton organization

Kosoff, Rachelle; Aslan, Joseph E.; Kostyak, John C.; Dulaimi, Essel; Chow, Hoi Yee; Prudnikova, Tatiana Y.; Radu, Maria; Kunapuli, Satya P.; McCarty, Owen J. T.; Chernoff, Jonathan

doi:10.1182/blood-2014-10-604504

Cited by 45 publications

(40 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To further examine Cdc42 signaling, we focused on group I p21‐activated kinases (Pak1/2/3), which are important effectors regulating cytoskeleton dynamics. Recently, Pak2 has been demonstrated to be important for platelet production . We observed that activation of Paks was stronger in TPO‐matured MKs when compared with the Lin − progenitors (Fig.…”

Section: Resultsmentioning

confidence: 62%

Cdc42‐dependent F‐actin dynamics drive structuration of the demarcation membrane system in megakaryocytes

Antkowiak

Viaud

Séverin

et al. 2016

Journal of Thrombosis and Haemostasis

View full text Add to dashboard Cite

EssentialsInformation about the formation of the demarcation membrane system (DMS) is still lacking. We investigated the role of the cytoskeleton in DMS structuration in megakaryocytes. Cdc42/Pak-dependent F-actin remodeling regulates DMS organization for proper megakaryopoiesis. These data highlight the mandatory role of F-actin in platelet biogenesis.Summary. Background: Blood platelet biogenesis results from the maturation of megakaryocytes (MKs), which involves the development of a complex demarcation membrane system (DMS). Therefore, MK differentiation is an attractive model for studying membrane remodeling. Objectives: We sought to investigate the mechanism of DMS structuration in relationship to the cytoskeleton. Results: Using three-dimensional (3D) confocal imaging, we have identified consecutive stages of DMS organization that rely on F-actin dynamics to polarize membranes and nuclei territories. Interestingly, microtubules are not involved in this process. We found that the mechanism underlying F-actin-dependent DMS formation required the activation of the guanosine triphosphate hydrolase Cdc42 and its p21-activated kinase effectors (Pak1/2/3). F€ orster resonance energy transfer demonstrated that active Cdc42 was associated with endomembrane dynamics throughout terminal maturation. Inhibition of Cdc42 or Pak1/2/3 severely destructured the DMS and blocked proplatelet formation. Even though this process does not require containment within the hematopoietic niche, because DMS structuration was observed upon thrombopoietin-treatment in suspension, integrin outside-in signaling was required for Pak activation and probably resulted from secretion of extracellular matrix by MKs. Conclusions: These data indicate a functional link, mandatory for MK differentiation, between actin dynamics, regulated by Cdc42/Pak1/2/3, and DMS maturation.

show abstract

Section: Resultsmentioning

confidence: 62%

Cdc42‐dependent F‐actin dynamics drive structuration of the demarcation membrane system in megakaryocytes

Antkowiak

Viaud

Séverin

et al. 2016

Journal of Thrombosis and Haemostasis

View full text Add to dashboard Cite

show abstract

“…WASp, Profilin, mDia1, Rho-GTPases). The recent studies on PaK2 highlight this as its phenotype is complex, with both actinand MT-dependent effects (Kosoff et al 2015). Furthermore, understanding how gene expression is regulated during platelet production, specifically the regulation of cytoskeletal-related proteins, will help us to provide a temporal context to their roles.…”

Section: Key Moleculesmentioning

confidence: 98%

Cytoskeletal regulation of platelet formation: Coordination of F-actin and microtubules

Poulter

Thomas

2015

The International Journal of Biochemistry & Cell Biology

View full text Add to dashboard Cite

Platelets are small, anucleate blood cells which play an important role in haemostasis. Thrombocytopenia is a condition where the platelet count falls below 150×10(9)/l and patients suffering from severe forms of this condition can experience life-threatening bleeds requiring platelet transfusions. Platelets are produced from large progenitor cells called megakaryocytes which are found in the bone marrow. The process of megakaryocyte maturation and the formation of proplatelets are essential steps in the production of mature platelets and both depend heavily on the actin and microtubule cytoskeletons. Understanding these processes is important for the development of in vitro platelet production which will help to treat thrombocytopenia as well as produce model systems for studying platelet-associated disorders. This review will highlight some of the recent advances in our understanding of the role of the cytoskeleton in platelet production, especially the key molecules and signalling pathways that regulate actin and microtubule crosstalk.

show abstract

“…Pak proteins have previously been implicated in both kinase-dependent and kinase-independent cytoskeletal remodeling in breast cancer and endothelial cell lines, in primary T cells, megakaryocytes, and neutrophils. 19,36,[42][43][44][45] In neurons, Pak regulates multiple downstream targets that influence actin-containing cell protrusions. Axon outgrowth is stimulated on laminin by partial inhibition of Pak-Pix interactions and inhibition of this complex also stimulates growth cone contacts.…”

mentioning

confidence: 99%

p21-activated kinase 2 regulates HSPC cytoskeleton, migration, and homing via CDC42 activation and interaction with β-Pix

Reddy

Radu

et al. 2016

Blood

Self Cite

View full text Add to dashboard Cite

• Pak2 kinase activity and b-Pix interaction regulate HSPC directional migration, actin remodeling, homing, and engraftment.• Pak2 regulates homing of HSPCs to the bone marrow via CDC42 activation.Cytoskeletal remodeling of hematopoietic stem and progenitor cells (HSPCs) is essential for homing to the bone marrow (BM). The Ras-related C3 botulinum toxin substrate (Rac)/ cell division control protein 42 homolog (CDC42) effector p21-activated kinase (Pak2) has been implicated in HSPC homing and engraftment. However, the molecular pathways mediating Pak2 functions in HSPCs are unknown. Here, we demonstrate that both Pak2 kinase activity and its interaction with the PAK-interacting exchange factor-b (b-Pix) are required to reconstitute defective Pak2 D/D HSPC homing to the BM. Pak2 serine/threonine kinase activity is required for stromal-derived factor-1 (SDF1a) chemokine-induced HSPC directional migration, whereas Pak2 interaction with b-Pix is required to regulate the velocity of HSPC migration and precise F-actin assembly. Lack of SDF1a-induced filopodia and associated abnormal cell protrusions seen in Pak2 D/D HSPCs were rescued by wild-type (WT) Pak2 but not by a Pak2-kinase dead mutant (KD). Expression of a b-Pix interaction-defective mutant of Pak2 rescued filopodia formation but led to abnormal F-actin bundles. Although CDC42 has previously been considered an upstream regulator of Pak2, we found a paradoxical decrease in baseline activation of CDC42 in Pak2 D/D HSPCs, which was rescued by expression of Pak2-WT but not by Pak2-KD; defective homing of Pak2-deleted HSPCs was rescued by constitutive active CDC42. These data demonstrate that both Pak2 kinase activity and its interaction with b-Pix are essential for HSPC filopodia formation, cytoskeletal integrity, and homing via activation of CDC42. Taken together, we provide mechanistic insights into the role of Pak2 in HSPC migration and homing. (Blood. 2016;127(16):1967-1975

show abstract

Pak2 restrains endomitosis during megakaryopoiesis and alters cytoskeleton organization

Abstract: Key Points Bone marrow-specific deletion of Pak2 is associated with macrothrombocytopenia and abnormal megakaryocyte morphology and function. Pak2 deletion is associated with defects in megakaryocyte endomitosis and the activation of Aurora-A and LIM kinase.

Cited by 45 publications

References 64 publications

Cdc42‐dependent F‐actin dynamics drive structuration of the demarcation membrane system in megakaryocytes

Cdc42‐dependent F‐actin dynamics drive structuration of the demarcation membrane system in megakaryocytes

Cytoskeletal regulation of platelet formation: Coordination of F-actin and microtubules

p21-activated kinase 2 regulates HSPC cytoskeleton, migration, and homing via CDC42 activation and interaction with β-Pix

Contact Info

Product

Resources

About