Biology subjects

Beachy, P. A.

Publications and source records attributed to Beachy, P. A..

3 recordsLinked to original sources

bioRxiv2021

LMO2 is critical for early metastatic events in breast cancer

Metastasis is responsible for the majority of breast cancer-related deaths, however identifying the cellular determinants of metastasis has remained challenging. Here, we identified a minority population of immature THY1+/VEGFA+ tumor epithelial cells in human breast tumor biopsies that display angiogenic features and are marked by the expression of the oncogene, LMO2. Higher abundance of LMO2+ basal cells correlated with tumor endothelial content and predicted poor distant recurrence-free survival in patients. Using MMTV-PyMT/Lmo2CreERT2 mice, we demonstrated that Lmo2 lineage- traced cells have a higher propensity to metastasize. LMO2 knockdown in human breast tumors reduced lung metastasis by impairing intravasation, leading to a reduced frequency of circulating tumor cells. Mechanistically, we find that LMO2 binds to STAT3 and is required for STAT3 activation by TNF and IL6. Collectively, our study identifies a population of metastasis-initiating cells with angiogenic features and establishes the LMO2-STAT3 signaling axis as a therapeutic target in breast cancer metastasis. One sentence summaryLMO2 modulates STAT3 signaling in breast cancer metastasis.

cancer biology↗

bioRxiv2020

Dispatched conformational dynamics couples transmembrane Na+ flux to release of lipid-modified Hedgehog signal

The DISP1 protein, related to the NPC1 and PTCH1 cholesterol transporters and to H+-driven transporters of the RND family, enables tissue patterning activity of the lipid-modified Hedgehog protein by releasing it from tightly-localized sites of embryonic expression. A 2.5 [A] resolution cryo-EM structure of DISP1 revealed three Na+ ions coordinated within a channel that traverses its transmembrane domain. This channel and Na+-binding are disrupted in DISP1-NNN (3.4 [A] resolution), a variant with isosteric substitutions for three intramembrane aspartates that each coordinate and neutralize charge for one of the three Na+ ions. DISP1-NNN and other variants that singly disrupt the Na+ sites retain binding to the lipid-modified Hedgehog protein, but most fail to export Hedgehog. The Sonic hedgehog signal (ShhN) interacts with the DISP1 extracellular domains (2.7 [A] complex structure), including an unusual extended DISP1 arm, at a location well above the membrane. Variability analysis reveals a dynamic series of DISP1 conformations, only a restricted subset of which appear to bind ShhN. The bound and unbound DISP1 conformations display distinct Na+ site occupancies; these differences, in conjunction with the unusual locations of certain lipids bound to DISP1, suggest a mechanism by which transmembrane Na+ flux may power extraction of the lipid-linked Hedgehog signal from the membrane, thus enabling its tissue patterning activity. The Na+-coordinating residues resolved in our DISP1 structures are wholly or partly conserved in some of the other metazoan RND family members, such as PTCH1 and NPC1, suggesting the utilization of Na+ flux to power their conformationally-driven activities.

biophysics↗

bioRxiv2018

Structural basis for cholesterol transport-like activity of the Hedgehog receptor Patched

Hedgehog protein signals mediate tissue patterning and maintenance via binding to and inactivation of their common receptor Patched, a twelve-transmembrane protein that otherwise would suppress activity of the seven-transmembrane protein, Smoothened. Loss of Patched function, the most common cause of basal cell carcinoma, permits unregulated activation of Smoothened and of the Hedgehog pathway. A cryo-EM structure of the Patched protein reveals striking transmembrane domain similarities to prokaryotic RND transporters. The extracellular domain mediates association of Patched monomers in an unusual dimeric architecture that implies curvature in the associated membrane. A central conduit with cholesterol-like contents courses through the extracellular domain and resembles that used by other RND proteins to transport substrates, suggesting Patched activity in cholesterol transport. Patched expression indeed reduces cholesterol activity in the inner leaflet of the plasma membrane, in a manner antagonized by Hedgehog stimulation and with implications for regulation of Smoothened.

biophysics↗