scholarly journals PINFORMED1 polarity in the shoot is insensitive to the polarity of neighbouring cells

2021 ◽  
Author(s):  
Abdul VK Kareem ◽  
Neha Bhatia ◽  
Carolyn Ohno ◽  
Marcus G Heisler
Keyword(s):  
Cell Polarity ◽  
Serine Threonine Kinase ◽  
Neighboring Cell ◽  
Threonine Kinase ◽  
Mechanical Signals ◽  
Mosaic Expression ◽  
Auxin Flux

Cell polarity patterns associated with plant phyllotaxis are thought to be determined by mechanical signals or auxin flux. Here we use mosaic expression of the serine threonine kinase PINOID (PID) in the shoot to investigate the flux hypothesis. We find that PID promotes changes in PIN1 polarity irrespective of initial or neighboring cell polarities, arguing against a role for flux in regulating phyllotaxis.

scholarly journals LKB1 kinase-dependent and -independent defects disrupt polarity and adhesion signaling to drive collagen remodeling during invasion

2016 ◽  
Vol 27 (7) ◽  
pp. 1069-1084 ◽  
Author(s):  
Jessica Konen ◽  
Scott Wilkinson ◽  
Byoungkoo Lee ◽  
Haian Fu ◽  
Wei Zhou ◽  
...  
Keyword(s):  
Cell Polarity ◽  
Cancer Metastasis ◽  
Kinase Activity ◽  
Rho Gtpase ◽  
Three Dimensional ◽  
Serine Threonine Kinase ◽  
Collagen Remodeling ◽  
Threonine Kinase ◽  
Three Dimensional Models

LKB1 is a serine/threonine kinase and a commonly mutated gene in lung adenocarcinoma. The majority of LKB1 mutations are truncations that disrupt its kinase activity and remove its C-terminal domain (CTD). Because LKB1 inactivation drives cancer metastasis in mice and leads to aberrant cell invasion in vitro, we sought to determine how compromised LKB1 function affects lung cancer cell polarity and invasion. Using three-dimensional models, we show that LKB1 kinase activity is essential for focal adhesion kinase–mediated cell adhesion and subsequent collagen remodeling but not cell polarity. Instead, cell polarity is overseen by the kinase-independent function of its CTD and more specifically its farnesylation. This occurs through a mesenchymal-amoeboid morphological switch that signals through the Rho-GTPase RhoA. These data suggest that a combination of kinase-dependent and -independent defects by LKB1 inactivation creates a uniquely invasive cell with aberrant polarity and adhesion signaling that drives invasion into the microenvironment.

scholarly journals STRADα Regulates LKB1 Localization by Blocking Access to Importin-α, and by Association with Crm1 and Exportin-7

2008 ◽  
Vol 19 (4) ◽  
pp. 1614-1626 ◽  
Author(s):  
Julia Dorfman ◽  
Ian G. Macara
Keyword(s):  
Catalytic Activity ◽  
Cell Polarity ◽  
Nuclear Export ◽  
Nucleocytoplasmic Transport ◽  
Cellular Distribution ◽  
Nucleocytoplasmic Shuttling ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Importin Α ◽  
Export Receptors

LKB1, a serine/threonine kinase, regulates cell polarity, metabolism, and cell growth. The activity and cellular distribution of LKB1 are determined by cofactors, STRADα and MO25. STRADα induces relocalization of LKB1 from the nucleus to the cytoplasm and stimulates its catalytic activity. MO25 stabilizes the STRADα/LKB1 interaction. We investigated the mechanism of nucleocytoplasmic transport of LKB1 in response to its cofactors. Although LKB1 is imported into the nucleus by importin-α/β, STRADα and MO25 passively diffuse between the nucleus and the cytoplasm. STRADα induces nucleocytoplasmic shuttling of LKB1. STRADα facilitates nuclear export of LKB1 by serving as an adaptor between LKB1 and exportins CRM1 and exportin7. STRADα inhibits import of LKB1 by competing with importin-α for binding to LKB1. MO25 stabilizes the LKB1–STRADα complex but it does not facilitate its nucleocytoplasmic shuttling. Strikingly, the STRADβ, isoform which differs from STRADα in the N- and C-terminal domains that are responsible for interaction with export receptors, does not efficiently relocalize LKB1 from the nucleus to the cytoplasm. These results identify a multifactored mechanism to control LKB1 localization, and they suggest that the STRADβ-LKB1 complex might possess unique functions in the nucleus.

Ability of PknA, a mycobacterial eukaryotic-type serine/threonine kinase, to transphosphorylate MurD, a ligase involved in the process of peptidoglycan biosynthesis

2008 ◽  
Vol 415 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Meghna Thakur ◽  
Pradip K. Chakraborti
Keyword(s):  
Protein Kinases ◽  
Solid Phase ◽  
Morphological Changes ◽  
Binding Assays ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Peptidoglycan Biosynthesis ◽  
Vitro Binding ◽  
Solid Phase Binding

Eukaryotic-type serine/threonine protein kinases in bacteria have been implicated in controlling a host of cellular activities. PknA is one of eleven such protein kinases from Mycobacterium tuberculosis which regulates morphological changes associated with cell division. In the present study we provide the evidence for the ability of PknA to transphosphorylate mMurD (mycobacterial UDP-N-acetylmuramoyl-L-alanine:D-glutamate-ligase), the enzyme involved in peptidoglycan biosynthesis. Its co-expression in Escherichia coli along with PknA resulted in phosphorylation of mMurD. Consistent with these observations, results of the solid-phase binding assays revealed a high-affinity in vitro binding between the two proteins. Furthermore, overexpression of m-murD in Mycobacterium smegmatis yielded a phosphorylated protein. The results of the present study therefore point towards the possibility of mMurD being a substrate of PknA.

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