Lucas Sullivan

Check out this great interview with a true rising star in metabolism research (and lab alumni)! 🙌

Mitochondrial calcium signaling regulates branched-chain amino acid catabolism in fibrolamellar carcinoma Mitochondrial Ca2+ signaling regulates branched-chain amino acid catabolism in an adolescent liver cancer.

Our paper on regulation of BCAA catabolism by mitochondrial calcium signaling is out!
Mitochondrial calcium signaling regulates branched-chain amino acid catabolism in fibrolamellar carcinoma | Science Advances www.science.org/doi/10.1126/...

[Person with ponytail wearing lab coat hands balloon to another person in front of a springboard, a magnet hanging from above, and then a target] PERSON WITH PONYTAIL to Person 2: Rub this balloon against your head, then go jump past that magnet toward the target on the wall. [caption] Before the bathroom scale was invented, the only way to weigh people was mass spectrometry.

Mass Spec

xkcd.com/3094/

Succinate Dehydrogenase loss causes cascading metabolic effects that impair pyrimidine biosynthesis - preLights Not all aspartate limitation is created equal: An aspartate biosensor reveals that inhibiting succinate dehydrogenase results in defects in pyrimidine synthesis and replication stress, unique from oth...

Niemi lab graduate student Hannah Pletcher recently joined @prelights.bsky.social and wrote nice highlight of recent work from @lucasbsullivan.bsky.social - check it out here!

Our latest, in Science Advances: In vivo CRISPR screen revealed sgRNAs that switch chemosensitive SCLC PDXs to become resistant.We validated KEAP1 as key hit and found KEAP1 alterations in IMpower133 trial, where active NRF2 links to reduced survival in chemo arm www.science.org/doi/10.1126/... 1/2

Overjoyed to have the opportunity to present my work orally at the Cancer Metabolism Showcase! Hope to see you there virtually!

From Nobel prize winning cancer researcher Bill Kaelin
Killing the Science Golden Goose - The American Journal of Medicine www.amjmed.com/article/S000...

Obliteride registeration opens today!!! Join the @lucasbsullivan.bsky.social team and help to CURE CANCER FASTER! See you August 9th at the starting line!! @obliteride.bsky.social #Obliteride #Obliteride2025 secure.fredhutch.org/goto/sulliva...

Hello, can you add me please?

Poster is printed! Looking forward to going to the Keystone Tumor Metabolism meeting next week in Vancouver. Come talk to me about NRF2, cysteine, and novel metabolite discovery! #KSTumorMetab25 #cancermetabolism #keystonesymposia

Seeing the world through the eyes of cultured cells The metabolic environment experienced by cultured cells often differs from physiological conditions. Here, we highlight the effects that the microenvironment can have on cultured cell behavior and adv...

happy to share our forum now online @Cell_Metabolism! fun for us (Guy & myself) to collaborate with @dfazakerley.bsky.social, Joycelyn, & Sam in putting together what we hope will be a useful piece for the broad metabolism community re: in vitro modeling! www.cell.com/cell-metabol...

YouTube video by KING 5 Seattle Potential NIH funding cuts could affect local cancer research

We were delighted to have @king5news.com.web.brid.gy visit us in the Termini Lab to discuss how NIH funding cuts could affect cancer research:

m.youtube.com/watch?v=Szo9...

We NEED indirect costs to provide funding needed complete research studies that will lead to life saving discoveries.

Thanks Jakub!

Thank you!

Thanks to Madeleine for wanting to stick around post-graduation to figure out “the boomerang” and the rest of the team for support, esp Kristian for quantitative efforts. Thanks to NIGMS and NCI for funding. Also, watch out for Madeleine's next act with @saranowinski.bsky.social!

TLDR – we find that, upon SDH loss, the combined effects of ASP depletion and succinate accumulation profoundly inhibit ATCase. Pyrimidine loss impairs ASP consumption for biosynthesis, causing ASP to accumulate until it outcompetes succinate to restart pyrimidines/biosynthesis once again.

The full paper has plenty more (ASP flux measurements, succinate sufficiency, replication stress), so I invite you to give it a full read. There are also fun phenotypes that epitomize some of the logical pitfalls that we metabolism nerds often warn about (e.g. levels =/= flux).

We found SDH impaired cells can reach >10 mM!

Conclusion: succinate competes with diminished ASP at ATCase, blocking pyrimidine synthesis. To our knowledge the first description of this relationship in cells + revealing another potential regulatory function of succinate.

Substrate specificity of aspartate transcarbamylase. Interaction of the enzyme with analogs of aspartate and succinate - PubMed The ability of aspartate transcarbamylase from Escherichia coli to catalyze carbamylation of amino acids other than the natural substrate, L-aspartate, was examined. Cysteine, cysteate, cysteinesulfin...

A literature search found a goldmine: E Coli ATCase was a workhorse of biochemistry for decades (e.g. ⬇️) One compound used to impair its function in vitro? Succinate! While the concentrations needed to impair ATCase in vitro seemed unrealistic at ~1+ mM...

pubmed.ncbi.nlm.nih.gov/3894357/

Rotenone treatment restores carb-Asp levels in AA5 treated cells (at a time point where Asp levels are near identical).

SDH inhibition is distinct from other mitochondrial impairments due to the accumulation of succinate, which we hypothesized to play a role. First, we decreased succinate production by cotreating with the CI inhibitor rotenone. Result: restoration of pyrimidine synthesis, even with comparable ASP.

Supplementing AA5 treated cells with uridine (Uri) but not asparagine (Asn) or adenine (Ade) prevents the ASP rebound effect.

So, what happens if we restore pyrimidines to these cells?

A complete loss of the ASP rebound and a return to the (very reasonable) phenotype of monotonic ASP depletion.

So, SDH loss causes a disproportionate effect on pyrimidine synthesis by impairing ATCase, but why?

Carbamoyl-Aspartate (carb-ASP) levels are depleted by AA5 treatment at 24 hours and remain depleted at 44 hours, when ASP levels had partially recovered.

We next investigated the biosynthetic fates of aspartate and found:

Aspartyl tRNA charge = OK

Purine nucleotides = OK

ASN = OK - Rebounds with ASP

Pyrimidine nucleotides = Depleted at the first step (ATCase, which makes Carb-ASP) - and stays depleted even with rebounding ASP:

Aspartate levels, measured by the GFP/NucRFP ratio, fall for about 24 hours upon AA5 treatment, then rebound.

When we did the same experiment with the SDH inhibitor AA5, we get a strange result:
ASP declines for ~24 hours until proliferation slows, then..ASP rebounds???

Even stranger:
Proliferation doesn't recover with ASP even though we know ASP supplementation would solve the proliferation defect!

ASP (measured by GFP) declines proportionally to environmental ASP availability in ASP auxotrophs (GOT1/2 DKO cells)

Deploying our ASP biosensor, jAspSnFR3, Madeleine & co used live cell imaging to continuously measure ASP levels (GFP) and cell number. In two cases – CI inhibition and GOT1/2 DKO cells, ASP levels crash over 24 hours then cell proliferation decays, leading to a new ~steady state.

Very reasonable.

Next, our 2nd preprint of the week (!), this one driven by @madelouhart.bsky.social

Previously: Mitochondrial inhibition impairs cell proliferation by constraining aspartate (ASP) availability.

Here: we investigate the kinetics of ASP depletion/ proliferation impairments and...surprises ensue!

Thanks Alex!

Re: ITS - the product number is in the methods. There are many "ITS" products available with different nutrient iterations, so check out our note about it (in the Methods) for more info. I would also be happy to discuss the details via DM/Zoom if you interested!

but it would be interesting to find out! If they don't activate, then investigating the salient metabolic/signaling differences for why not could reveal new, manipulable biology. Or at least, that is the hope!

Thanks Dylan!

Almost certainly many effects in many systems, which (to me) is exactly the point. Neither FBS nor defined media = physiological, but comparisons across them (+other environments) could be illuminating. Would macrophages proliferate or activate in defined media? We don't know...

Update to tag the author (and new arrival to bsky) - @olivernewsom.bsky.social!