Biology subjects

Mott, H. R.

Publications and source records attributed to Mott, H. R..

3 recordsLinked to original sources

bioRxiv2026

Structural basis of the protein kinase PKN1 HR1 domain oligomerization and differential regulation by RhoA and Rac1

The protein kinase C-related kinase (PKN) family of serine/threonine kinases consists of PKN1, PKN2 and PKN3, all of which are Rho family GTPase effectors. PKNs have three N-terminal Homology Region 1 (HR1) domains (HR1a, HR1b and HR1c), which form antiparallel coiled coils, which in two cases interact with Rho family GTPases, activating the kinase. The PKNs are implicated in several important cellular processes, including cytoskeletal regulation, cell adhesion, gene expression and cell cycle progression, and are also implicated in cancer. Here we have investigated the roles of the HR1 domains in PKN oligomerisation. We show that PKN1 HR1a is a dimer and that the HR1c domain drives further oligomerization. We have mapped the interactions between the HR1 domains and used an integrative approach to model HR1-containing PKN1 dimers. Biophysical analysis shows that RhoA forms a 1:2 complex with HR1a, resulting in a rearrangement of the HR1a dimer, an outcome supported by SAXS models. In contrast, Rac1 binds to monomeric HR1a, suggesting that this GTPase activates PKN1 via a different mechanism. These data provide structural insight into interactions between HR1 domains and the Rho family proteins and their potential consequences for PKN1 activation.

biophysics↗

bioRxiv2022

The Cdc42 effector and non-receptor tyrosine kinase, ACK defines a distinct STAT5 transcription signature in a chronic myeloid leukaemia cell model

Activated Cdc42-associated kinase (ACK) is a Rho family effector that is widely implicated in cancer. Here, we describe new roles for ACK in transcriptional regulation mediated by its relationship with the signal transducer and activators of transcription (STAT) family. We show that ACK can interact with STAT3, STAT5A and STAT5B, and augments phosphorylation at the conserved activation tyrosine on these STAT members. ACK stimulates oncogenic STAT nuclear relocation and transcriptional activation. We also identify endogenous relationships between ACK and STAT family members in haematopoietic disease cell lines. In the K562 chronic myeloid leukaemia cell line, we confirm that ACK contributes to the pool of active, nuclear STAT5. By interrogating ACK knock out cells we describe an ACK-driven STAT5 transcriptional signature in K562s. We propose ACK as a contributor to hyperactivated STAT5 signalling in this CML cell line and reveal a new route for therapeutic intervention. O_FIG O_LINKSMALLFIG WIDTH=178 HEIGHT=200 SRC="FIGDIR/small/494364v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1c4973dorg.highwire.dtl.DTLVardef@1a54ba1org.highwire.dtl.DTLVardef@1083bf9org.highwire.dtl.DTLVardef@1997ad0_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2019

Assembly of novel, nuclear dimers of the PI3-Kinase regulatory subunits underpins the pro-proliferative activity of the Cdc42-activated tyrosine kinase, ACK

The tyrosine kinase ACK is an oncogene associated with poor prognosis in human cancers. ACK promotes proliferation, in part, by contributing to the activation of Akt, the major PI3-Kinase effector. We show that ACK also regulates PI3-Kinase directly, via interactions with the PI3-Kinase regulatory subunits. ACK interacts with all five regulatory subunit isoforms and directly phosphorylates p85, p85{beta}, p55 and p50 on Tyr607 (or equivalent). Phosphorylation of p85{beta} at this residue promotes cell proliferation but, counterintuitively, ACK does not stimulate PI3-Kinase catalytic activity. We show that ACK stabilizes p85 levels by promoting an interaction between the p85 nSH2 domain and pTyr607, protecting p85 from ubiquitination. We demonstrate that ACK interacts with p85 exclusively in nuclear-enriched cell fractions where the increased levels of the regulatory subunits, together with the nSH2-pTyr607 interaction, promote formation of dimeric p85. We postulate that these novel dimers undertake nuclear functions that contribute to Cdc42-ACK driven oncogenesis. We propose that ACK shapes PI3-Kinase signalling by dampening the PIP3 response, whilst continuing to drive cell proliferation through Akt activation and hereto unexplored but crucial functions of nuclear dimeric p85. These new regulatory subunit dimers represent a previously undescribed mode of regulation for PI3-Kinase and potentially reveal additional avenues for therapeutic intervention.

molecular biology↗