dictyNews

Electronic Edition

Volume 49, number 13

May 19, 2023



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Abstracts

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The protein kinases of Dictyostelia and their incorporation into 

a signalome.



Koryu Kin1,3, Zhi-hui Chen1, Gillian Forbes1,4, Hajara Lawal1, 

Christina Schilde1,5, Reema Singh1,2,6, Christian Cole2,7, 

Geoffrey J. Barton2 and Pauline Schaap1*



1Molecular Cell and Developmental Biology, School of Life 

Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom

2Computational Biology, School of Life Sciences, University of 

Dundee, Dundee DD1 5EH, United Kingdom, 





Cellular Signalling, in press



Protein kinases are major regulators of cellular processes, but the 

roles of most kinases remain unresolved. Dictyostelid social 

amoebas have been useful in identifying functions for 30% of its 

kinases in cell migration, cytokinesis, vesicle trafficking, gene 

regulation and other processes but their upstream regulators and 

downstream effectors are mostly unknown. Comparative genomics 

can assist to distinguish between genes involved in deeply conserved 

core processes and those involved in species-specific innovations, 

while co-expression of genes as evident from comparative 

transcriptomics can provide cues to the protein complement of 

regulatory networks. Genomes and developmental and cell-type 

specific transcriptomes are available for species that span the 0.5 

billion years of evolution of Dictyostelia from their unicellular ancestors. 

In this work we analysed conservation and change in the abundance, 

functional domain architecture and developmental regulation of protein 

kinases across the 4 major taxon groups of Dictyostelia. All data are 

summarized in annotated phylogenetic trees of the kinase subtypes 

and accompanied by functional information of all kinases that were 

experimentally studied. We detected 393 different protein kinase 

domains across the five studied genomes, of which 212 were fully 

conserved. Conservation was highest (71 %) in the previously defined 

AGC, CAMK, CK1, CMCG, STE and TKL groups and lowest (26%) in 

the "other" group of typical protein kinases. This was mostly due to 

species-specific single gene amplification of “other” kinases. Apart 

from the AFK and alpha-kinases, the atypical protein kinases, such 

as the PIKK and histidine kinases were also almost fully conserved. 

The phylogeny-wide developmental and cell-type specific expression 

profiles of the protein kinase genes were combined with profiles from 

the same transcriptomic experiments for the families of G-protein 

coupled receptors, small GTPases and their GEFs and GAPs, the 

transcription factors and for all genes that upon lesion generate a 

developmental defect. This dataset was subjected to hierarchical 

clustering to identify clusters of co-expressed genes that potentially 

act together in a signalling network. The work provides a valuable 

resource that allows researchers to identify protein kinases and other 

regulatory proteins that are likely to act as intermediates in a network 

of interest.



Submitted by Pauline Schaap [[log in to unmask]]

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A phosphatidylinositol phosphate kinase inhibits Ras activation and 

regulates chemorepulsion in Dictyostelium discoideum



Sara A. Kirolos, Chance E. Hatfield, Ryan J. Rahman, Kristen M. 

Consalvo, Nolan K. Dittenhauser, and Richard H. Gomer





J. Cell Science, in press



During developmental and immune responses, cells move towards or 

away from some signals. Although much is known about chemoattraction, 

chemorepulsion (the movement of cells away from a stimulus) remains 

poorly understood. Proliferating Dictyostelium discoideum cells secrete a 

chemorepellent protein called AprA. Examining existing knockouts, we 

identified proteins required for AprA-induced chemorepulsion, and a

 genetic screen suggested that the enzyme phosphatidylinositol 

phosphate kinase A (PIPkinA) may also be needed for chemorepulsion. 

Here we show that cells lacking PIPkinA are not repelled by AprA, and 

that this phenotype is rescued by expression of PIPkinA. To bias cell 

movement, AprA inhibits Ras activation at the side of the cell closest to 

the source of AprA, and we find that PIPkinA is required for AprA to inhibit 

Ras activation. PIPkinA decreases levels of the phosphatidylinositol 

phosphates PI(4)P and PI(3,4,5)P3, and possibly because of these effects, 

potentiates phagocytosis and inhibits cell proliferation. Cells lacking 

PIPkinA show normal AprA binding, suggesting that PIPkinA regulates 

chemorepulsion at a step between the AprA receptor and AprA 

inhibition of Ras activation.





Submitted by Richard Gomer[[log in to unmask]]

_____________________________________________________





Enhanced Sestrin expression through Tanshinone 2A treatment i

mproves PI3K-dependent inhibition of glioma growth 



Judith Schaf1*, Sonia Shinhmar1*, Qingyu Zeng2, Olivier Pardo3, 

Philip Beesley1, Nelofer Syed2 and Robin SB Williams1¥



1 Centre for Biomedical Sciences, School of Biological Sciences, 

Royal Holloway University of London, Egham, TW20 0EX, UK. 

2 John Fulcher Neuro-Oncology Laboratory, Imperial College 

London, Hammersmith Hospital, London, UK. 

3 Division of Cancer, Department of Surgery and Cancer, Imperial 

College London, London, UK.



Cell Death Discovery, in press



Glioblastomas are a highly aggressive cancer type which respond 

poorly to current pharmaceutical treatments, thus novel therapeutic 

approaches need to be investigated. One such approach involves 

the use of the bioactive natural product tanshinone IIA (T2A) derived 

from the Chinese herb Danshen, where mechanistic insight for this 

anti-cancer agent is needed to validate its use. Here, we employ a 

tractable model system, Dictyostelium discoideum, to provide this 

insight. T2A potently inhibits cellular proliferation of Dictyostelium, 

suggesting molecular targets in this model. We show that T2A rapidly 

reduces phosphoinositide 3 kinase (PI3K) and protein kinase B (PKB) 

activity, but surprisingly, the downstream complex mechanistic target 

of rapamycin complex 1(mTORC1) is only inhibited following chronic 

treatment. Investigating regulators of mTORC1, including PKB, 

tuberous sclerosis complex (TSC),and AMP-activated protein kinase 

(AMPK), suggests these enzymes were not responsible for this effect, 

implicating an additional molecular mechanism of T2A. We identify this 

mechanism as the increased expression of sestrin, a negative 

regulator of mTORC1. We further show that combinatory treatment 

using a PI3K inhibitor and T2A gives rise to a synergistic inhibition of 

cell proliferation. We then translate our findings to human and mouse-

derived glioblastoma cell lines, where both a PI3K inhibitor (Paxalisib) 

and T2A reduces glioblastoma proliferation in monolayer cultures and 

in spheroid expansion, with combinatory treatment significantly 

enhancing this effect. Thus, we propose a new approach for cancer 

treatment, including glioblastomas, through combinatory treatment 

with PI3K inhibitors and T2A.





Submitted by Robin Williams [[log in to unmask]]

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[End dictyNews, volume 49, number 13]