Biology subjects

Thacker, S.

Publications and source records attributed to Thacker, S..

3 recordsLinked to original sources

bioRxiv2022

Structural and Dynamic Effects of PTEN C-terminal Tail Phosphorylation

The phosphatase and tensin homolog deleted on chromosome ten (PTEN) tumor suppressor gene encodes a tightly regulated dual-specificity phosphatase that serves as the master regulator of PI3K/AKT/mTOR signaling. The carboxy-terminal tail (CTT) is key to regulation and harbors multiple phosphorylation sites (Ser/Thr residues 380-385). CTT phosphorylation suppresses the phosphatase activity by inducing a stable, closed conformation. However, little is known about the mechanisms of phosphorylation-induced CTT-deactivation dynamics. Using explicit solvent microsecond molecular dynamics simulations, we show that CTT phosphorylation leads to a partially collapsed conformation, which alters the secondary structure of PTEN and induces long-range conformational rearrangements that encompass the active site. The active site rearrangements prevent localization of PTEN to the membrane, precluding lipid phosphatase activity. Notably, we have identified phosphorylation-induced allosteric coupling between the interdomain region and a hydrophobic site neighboring the active site in the phosphatase domain. Collectively, the results provide a mechanistic understanding of CTT phosphorylation dynamics and reveal potential druggable allosteric sites in a previously believed clinically undruggable protein.

biophysics↗

bioRxiv2021

Redefining the PTEN Promoter: Identification of Two Upstream Transcription Start Regions

Germline mutation of PTEN is causally observed in Cowden syndrome (CS) and is one of the most common genetic causes of autism spectrum disorder (ASD). However, the majority of individuals who present with CS-like clinical features are found to be PTEN-mutation negative. Reassessment of PTEN promoter regulation may help explain abnormal PTEN dosage, as only the minimal promoter and coding regions are currently included in diagnostic PTEN mutation analysis. We reanalyzed the architecture of the PTEN promoter using next-generation sequencing datasets. Specifically, run-on sequencing assays identified two additional TSRs at -2052 and -1907 basepairs from the start of PTEN, thus redefining the PTEN promoter and extending the PTEN 5UTR. The upstream TSRs described are active in cancer cell lines and human cancer and normal tissue. Further, these TSRs can produce novel PTEN transcripts due to the introduction of new splice sites. Evaluation of transcription factor binding specific to the upstream TSRs shows overrepresentation of TFs involved in inflammatory processes. Together, these data suggest that potentially clinically relevant promoter variants upstream of the known promoter may be overlooked in indivduals considered PTEN germline mutation-negative and may also explain lack of PTEN expression in sporadic neoplasias without PTEN somatic structural defects.

genetics↗

bioRxiv2018

Limb- and tendon-specific Adamtsl2 deletion identifies a soft tissue mechanism modulating bone length

Disproportionate distal limb shortening is the hallmark of acromelic dysplasias. Among them, geleophysic dysplasia is a rare, frequently lethal condition characterized by severe short stature, musculoskeletal, cardiac, pulmonary, and skin anomalies. Geleophysic dysplasia results from dominant fibrillin-1 (FBN1) or recessive ADAMTSL2 mutations, suggesting a functional link between ADAMTSL2 and FBN1. Mice lacking ADAMTSL2 die at birth, precluding analysis of postnatal skeletal growth and mechanisms underlying the skeletal anomalies of geleophysic dysplasia. We show that Adamtsl2 is expressed in limb soft tissues, predominantly in tendon. Expression in developing bones is limited to their terminal cell layers that are destined to become articular cartilage and is absent in growth plate cartilage. Adamtsl2 conditional deletion in limb mesenchyme using Prxl-Cre led to an acromelic dysplasia, providing a suitable model for investigation of geleophysic dysplasia. Unexpectedly, conditional Adamtsl2 deletion using Scx-Cre, a tendon-specific deleter, also impaired skeletal growth. Specific morphogenetic anomalies were seen in Achilles tendon, along with FBN1 accumulation. Thus, ADAMTSL2, shown here to bind fibrillin microfibrils in vitro, limits fibrillin microfibril formation in tendons and promotes tendon growth. The findings suggest that reduced bone growth in geleophysic dysplasia results from external tethering by short tendons rather than intrinsic growth plate anomalies.

developmental biology↗