Marcus Harrell

PhD Candidate in @daslab_pombe lab at Boston College

[ASAPbio @ASAPbio_]

Meet your colleagues and discuss a new preprint over lunch during #cellbio2023 🥳

We’re pleased to announce preprint launch parties organized by ASAPbio on Dec 4 & 5 in Boston, MA, USA!

[ASAPbio @ASAPbio_]

@jwadeharperlab @HarvardCellBio @TaraEssockBurns @dave_matus @ArcadiaScience Preprint launch party (Boston) Tue Dec 5, 1-2pm | Marcus Harrell @DasLab_Pombe | The Arp2/3 complex promotes periodic removal of Pak1-mediated negative feedback to facilitate anticorrelated Cdc42 oscillations: https://t.co/D3YbBu92GL

RSVP: https://t.co/7XB49buoeA
#cellbio2023

[Marcus Harrell @MarcusHarrell12]

@EmmaKoory See you at ASCB for sure!

[Marcus Harrell @MarcusHarrell12]

Our models suggest that there is a phase shift between the accumulation of Cdc42, Scd1, and Scd2 (Positive feedback loop) and Pak1 (time-delayed negative feedback). Indeed, we were able to capture these shifts in vivo. (Colors correspond to protein of interest) (12/17)

[Marcus Harrell @MarcusHarrell12]

@Haylee_Grace Thanks Haylee! A beautiful and intricate one!

[Marcus Harrell @MarcusHarrell12]

@debalina_rockz @biorxiv_cellbio @bethfcampbell1 @hongtian162 @DasLab_Pombe Thanks Deb!

[Marcus Harrell @MarcusHarrell12]

I am pleased to announce that my first manuscript as fist author is now posted on @biorxiv_cellbio. Thank you to Ziyi Liu (co-first author), @bethfcampbell1, Livi Chinsen, @hongtian162 and especially to my graduate mentor Dr. Maitreyi Das @DasLab_Pombe (1/17)

[Marcus Harrell @MarcusHarrell12]

@jboerckel @biorxiv_cellbio @bethfcampbell1 @hongtian162 @DasLab_Pombe Thank you!

[Marcus Harrell @MarcusHarrell12]

To read more about our work, please read our preprint which I have linked here: https://t.co/fLFijkqGHk
(17/end)

[Marcus Harrell @MarcusHarrell12]

And while much work has established the impact of Cdc42 on membrane trafficking, we are now showing that membrane trafficking, in turn, directly regulates Cdc42 activity. (16/17)

[Marcus Harrell @MarcusHarrell12]

Further, we show the regulatory relationship between Pak1 and endocytosis. We find that Pak1 is removed from the membrane as endocytic vesicles internalize and, simultaneously, Pak1 activity is required for proper vesicle internalization. (11/17)

[Marcus Harrell @MarcusHarrell12]

Anticorrelated oscillations are the result of positive feedback (Scd1 & Scd2) and time-delayed negative feedback (via the Pak1 kinase). The anticorrelated patterning also suggests that the ends must compete for Cdc42 activity. (5/17)

[Marcus Harrell @MarcusHarrell12]

We find that endocytosis is required for proper Cdc42 activity between ends. Using in vivo experiments alongside mathematical modeling, we show that Pak1 stabilizes at a cell end when endocytosis is disrupted, preventing the return of Scd1. (Model in insets) (10/17)

[Marcus Harrell @MarcusHarrell12]

Normally, Arp2/3 is required for endocytosis to recycle protein from the membrane in yeast. But, surprisingly, localization of the Cdc42 activator Scd1 and its scaffold Scd2 are significantly decreased when the Arp2/3 complex is inhibited. (9/17)

[Marcus Harrell @MarcusHarrell12]

Unexpectedly, we find that cells are no longer able to reestablish Cdc42 activity at a second end when the Arp2/3 complex and branched actin were disrupted. (8/17)

[Marcus Harrell @MarcusHarrell12]

we observed that F-actin structures (branched actin and actin cables) are required for oscillations. So, we asked is competition for Cdc42 wired or wireless? Is it dependent on cables (which span the cell like phone lines) or branched actin (which don’t contact both ends)? (7/17)

[Marcus Harrell @MarcusHarrell12]

Disruption to these oscillation patterns means Cdc42 regulation is disrupted! So, we use the oscillations to study Cdc42 regulation. (6/17)