SUMO Proteins Emerge as Critical K2P Channel Regulators

In memory of Dan Getz (1969-2006) and sponsored by the Dan Getz Endowed Fund for Heart Disease Research, the most recent lecture in the Heart Research Series was presented on Wednesday afternoon. For the many that were in attendance, Dr. Steve Goldstein, the newly appointed Provost of the university, presented a wonderful story on his ongoing research involving K2P channels. The ubiquitously expressed K2P channels are critical in regulating a cell’s resting membrane potential, making them essential for the proper function of any cell that operates through electrical stimulation. His research has uncovered the surprising result that the activity of these elusive channels is regulated by small ubiquitin-like modifier (SUMO) proteins. Sumoylation was widely thought to only occur in the nucleus, but a number of elegantly designed experiments proved that this is not the case. The recent finding that the activity of these channels is modulated by sumoylation uncovers an entirely new way of thinking about K2P channel activity. Although the research presented was focused on specific isoforms of the channel, Dr. Goldstein’s results will extend to aid research involved with trying to understand diseases of the heart and beyond.

Colocalization of SUMO1 and K2P1 at the plasma membrane, from Plant et al. PNAS 107(23): 10743–10748, 2010.

Three Leopards and a Shower

Dan Perlman passed along these notes from Briana Abrahms ’08, a Brandeis physics major whose focus has shifted to conservation issues and is in currently working in Botswana. Briana’s blog has more information, you can read it at http://www.conservationconnections.blogspot.com/

My Crash Course in Large Carnivores (Aug. 1, 2011)

Dear family and friends,

Greetings from Botswana! As many of you know, I’ve taken a six-month research position with the Botswana Predator Conservation Trust (BPCT) located outside the Moremi Game Reserve in northwestern Botswana. BPCT is a non-profit organization that works closely with the Botswana government to study and protect Botswana’s five large carnivores: lions, hyenas, African wild dogs, leopards, and cheetahs. (Read more at www.bpctrust.org!) A quick note about African wild dogs because its name can cause some confusion: African wild dogs are a distinct species (Lycaon pictus) just like the Gray wolf or the Spotted hyena, and do not refer to feral dog populations, as the name suggests. Because of habitat loss, disease, and competition with other carnivores, African wild dogs are one of the most endangered predators in Africa, with less than 1% of its former population remaining.

Within each of the five species that BPCT studies, several ‘representatives’ – usually one of the dominant animals in a pack – are radio collared and collect GPS data on their movements. So most of what we do on a day-to-day basis is drive around, see what animals we can pick up with our radio antennae, and then track them. We are the only organization who are permitted to go off road to look for animals, so we do a lot of exciting off-roading into the bush! Once we find the animal(s), we download the GPS data from its collar and make observations about what they are doing (eating, hunting, resting, caring for offspring, etc.) and what other animals it’s with at that time. The purpose of this is to collect data on the basic ecology and behavior of these species, for example: How much space does this species use? How does it share the landscape with other species? What does it eat? How do animals rise to dominance in a pack? The list goes on and on.

I got incredibly lucky on my first day here to witness a successful wild dog hunt that led to a steenbok kill (steenboks are like little antelope). Apparently this is really rare to see – the director of BPCT who’s been working here for over 20 years says he can count on one hand the number of times he’s seen a wild dog kill. And I saw it on my first day! Here’s a crudely edited video that I took with my camera, with footage of the camp I’m staying at, the wild dog hunt, and some of the other things I’ve seen. Be sure to check it out and notice the radio collars on some of the animals. Warning!: the video includes lions copulating and wild dogs killing and eating the steenbok, which can be a bit gruesome. (If the link doesn’t work for you, just search for ‘Botswana Day 1 – Wild Dog Hunt’ on YouTube).

A Tale of Three Leopards and a Shower (Oct. 15, 2011)

Hi all!

Here goes again with another monthly email. Last night I had what was probably my most exciting night at dog camp. Now that the dry season is in full swing here, we’ve been seeing more non-human visitors to our camp in search of water, which is generally found either in a bird bath near our kitchen area or our shower. Yesterday evening I came back from the field and met my coworkers Krys and Neil on their way out to find Chalak, a collared male leopard whose signal they had picked up very close to camp. We’d been very eager to find him because earlier this week he’d been seen mating with not one but TWO uncollared females within minutes of each other, which is very unusual because leopards are solitary and same-sexes generally don’t tolerate each other, at least from what BPCT researchers have seen.

Sure enough, about a half hour later I got a radio message from Krys saying they’d found Chalak and his two lady friends walking towards camp. It was dark by then, and I was alone in camp getting dinner ready in the kitchen. A few minutes later, I hadn’t heard anything more from Krys, but I did hear the loud snarling noise that one only hears when leopards are mating close by. It was obvious that they were somewhere in camp, though I couldn’t see them. The good thing was that I could localize where Chalak and one of the females were from the sounds of their mating, but I had no idea where the other female was.

As I stood in the kitchen near our radio, that question was solved as I saw one of the females emerge out of the bushes and head over to our bird bath, twenty feet away from where I was standing. Our kitchen (which is open, no walls) was the only structure around and there was nowhere safer for me to go, so I radioed Krys to let her know the situation and then I stayed put and kept an eye on the female. She didn’t seem interested in my presence. Then, just a few minutes later, I saw Chalak follow her out of the bushes and lay down by the bird bath. That really got my heart going – Chalak is a huge leopard, almost twice the size of the females, and I was standing twenty feet away from him with nothing in between. Again, though, his promiscuous evening had made him very thirsty and he was only interested in getting some water. After a few more minutes, the other female came, so now camp was occupied by three leopards and myself by my lonesome! I had quite the adrenaline rush. Not long after Krys and Neil finally came and pulled the truck right up to the kitchen. I climbed over a fridge in order to not exit the kitchen near the leopards and hopped into the truck. That was a huge relief. We tried to scare Chalak and the females off with the car to discourage them from using our camp as a drinking hole, but Chalak was so habituated to cars that he wasn’t bothered by it approaching him. Eventually he and the females made their way to the shower, where we heard some (probably hot and steamy) leopard mating roars. Krys and Neil ended up driving me to my tent and then parking the truck next to their tent so nobody had to walk around by themselves. This morning the leopards were out of camp but I saw one of them from my tent in the grassland behind camp, so they are still around. And thus the saga continues!

On another note, I decided to make a little “Day in the Life” video (shot very unprofessionally with my tiny digital camera) to hopefully give you a better sense of what I actually do here, how I spend my time, etc. I made this on October 7th, which turned out to be a pretty good day to choose for this project. Enjoy!

Cheers,
Briana

Quantitative Biology Lecture Prize

The Quantitative Biology Program at Brandeis University, supported by a grant from Howard Huges Medical Institute, is now soliciting applications for an award for preparing an outstanding set of three pedagogical lectures on a subject at the interface of the physical and biomedical sciences.  These lectures will be given at the Quantitative Biology Boot camp, January 12, through Friday, January 13, 2012.  The award consists of a cash prize of $2,000.

Any graduate student or postdoctoral research associate currently at Brandeis is eligible to apply.  The application packet should consist of short/ curriculum vitae/ and a one page outline of the three lectures.  QB faculty will work with the successful applicant in preparing the lectures.  Applications should be submitted  to Jen Scappini either by campus mail (MS009), or e-mail (jscappin@brandeis.edu). (Due date will be discussed at the Wednesday, 10.19.11 Meeting).

An information session for potential applicants will be held on Wednesday, October 19th, 2:30-3:00 in Kosow 207.

Biotech/Science Forum (Oct. 18)

On October 18, the Brandeis Hiatt Career Center will hold its third annual event focused on helping students at Brandeis in the sciences learn about important professional trends and speak with over 25 alumni and professionals who were once in their shoes.  The event is appropriate for those who seek insights about careers and trends in research, or simply want to learn about what alumni are doing now.

3rd Annual Biotech, Healthcare & Science Forum
“Discovery without Borders.
Sponsored by the Hiatt Career Center
Tuesday, Oct. 18, 2011
6:00 – 9:00 p.m. – Formal program, Sherman Hall, Hassenfeld
6pm: Panel
7pm: Networking

Features
– Expert panel moderated by Provost Steve Goldstein ’78
– Followed by chance to speak with 25+ alumni who are coming to help

Complete Event & RSVP Details: go.brandeis.edu/biotech

Register promptly, as this event fills up every year.

Horwitz Prize for Hall, Rosbash and Young

Columbia University will award the 2011 Louisa Gross Horwitz Prize to Jeffrey C. Hall, Michael Rosbash, and Michael W. Young “for their work on the molecular basis of circadian rhythms, the first demonstration of a molecular mechanism for behavior”. Hall is a Professor Emeritus of Biology at Brandeis, and Rosbash is an HHMI Investigator and Professor of Biology at Brandeis. The prize is awarded annually for outstanding basic research in biology or biochemistry. In the early 1980s, working at Brandeis, Hall and Rosbash combined their expertise in fly genetics and molecular biology to clone the Drosophila gene period, a key regulator of the circadian rhythm, as Young and his lab at The Rockefeller University did independently.

In subsequent years, research in the Hall and Rosbash labs at Brandeis led to transcriptional feedback models for the clock, discovery of additional genetic factors involved in the behavior, and discovery of neuroanatomical features involved in circadian rhythms. Circadian rhythms have been found in a very wide variety of organisms, and seem to be important in metabolism and disease.

Hall and Rosbash will receive their award in November at  a ceremony at Columbia University.

Formins require assistance; not so different from other actin nucleators

Formins are a family of proteins conserved across a wide range of eukaryotes and constitute a major class of actin nucleators. In a paper recently published in Molecular Biology of the Cell, a team led by Ph.D. student Brian Graziano in the laboratory of Professor Bruce Goode made the surprising finding that formins depend on co-factors to efficiently nucleate actin assembly both in vitro and in vivo. This discovery was unanticipated because earlier studies had shown that purified formins are sufficient to catalyze actin polymerization in vitro. Graziano, working in collaboration with the labs of Laurent Blanchoin and Isabelle Sagot, investigated the mechanism and function of a formin-binding protein called Bud6 and found that it elevates formin nucleation activity by 5-10 fold. Further, they showed that this activity of Bud6 is critical in vivo for maintaining normal levels of actin cable assembly and polarized cell growth (see figure).

Earlier work from the Goode lab had shown that Bud6 enhances formin-mediated actin assembly in vitro (Moseley et al., 2004), but had left open the question of whether Bud6 stimulates the nucleation or elongation phase of filament growth (an important mechanistic distinction), and whether the activities of Bud6 are important in vivo. Graziano and collaborators dissected Bud6 mechanism by: (a) generating mutations in Bud6 that separately disrupt its interactions with formins (bu6-35) and actin monomers (bud6-8), (b) using TIRF (total internal reflection fluorescence) microscopy to visualize the effects of Bud6 and formins on individual actin filaments polymerizing in real time, and (c) performing a genetic analysis of bud6 alleles. They made three important observations. First, Bud6 enhances the nucleation rather than elongation phase of actin assembly, in sharp contrast to another formin ligand, profilin, that enhances elongation. Second, this activity of Bud6 requires its direct interactions with both the formin and actin monomers, suggesting that Bud6 recruits monomers to the formin to help assemble an actin ‘seed’. Third, genetic perturbation of these activities of Bud6 results in reduced levels of actin cable formation in vivo, in turn causing defects in polarized secretion and cell growth.

Until now, formins were thought to nucleate actin assembly by themselves, which is mechanistically distinct from the Arp2/3 complex (another major actin nucleator). Efficient nucleation by Arp2/3 requires the addition of a nucleation-promoting factor (NPF) such as WASp or WAVE, which recruits actin monomers. Graziano et al. reveal that some formins are similar to Arp2/3 in that they too require an NPF for robust nucleation. Their findings also uncover unanticipated mechanistic parallels between the two systems, since in each case nucleation requires both an actin filament end-capping component (formin or Arp2/3) and an actin monomer-recruiting factor (Bud6 or WASp).

How well is this formin-NPF mechanism conserved? Clues to this question have recently emerged from other studies. A paper published last year in The Journal of Cell Biology by the Goode lab, working in collaboration with the labs of Niko Grigorieff (Brandeis) and Gregg Gundersen (Columbia), implicates the human tumor suppressor protein Adenomatous polyposis coli (APC) in functioning as a formin NPF (Okada et al., 2010). Another study published in The Proceedings of the National Academy of Sciences by the labs of Mike Eck (Dana Farber Cancer Institute), Margot Quinlan (UCLA), and Avital Rodal (Brandeis), suggests that Spire, which is conserved in mammals and flies, may serve as a formin NPF (Vizcarra et al., 2011). Bud6, Spire, and APC all bind multiple actin monomers and interact with the C-terminus of formins to enhance actin assembly, suggesting that they may have related mechanisms and perform functionally analogous roles.

Although the requirement of NPFs increases the complexity of the formin mechanism, it offers an explanation for how cells simultaneously overcome two prominent barriers to actin assembly found in vivo – actin monomer binding proteins (e.g. profilin) that suppress formation of an actin nucleus and capping proteins that terminate growth by associating with the growing end of the filament. NPFs can facilitate nucleation by recruiting actin monomers in the presence of profilin, and formins protect growing ends of filaments from capping proteins. Future work will focus on identifying new formin-NFP pairs, defining the cellular processes with which they are associated, and distinguishing the underlying mechanistic differences among each set.

XJ Wang, Ranjan Sen return to Brandeis for lectures in October

Former Brandeis faculty members Xiao-Jing Wang (Physics, Neuroscience) and Ranjan Sen (Biology, Rosenstiel Center) will be back on campus next week to give seminars. Wang, now in the Department of Neurobiology and Kavli Institute for Neuroscience at the Yale University School of Medicine, will speak twiceon Monday, Oct 3. At 11:00 am in Volen 201, he will present “Context-dependent decision making” at Computational/Systems Neuroscience Journal Club, followed by a talk at 3:45 pm in Gzang 121, discussing “A ‘cognitive-type’ cortical microcircuit: decision-making and short-term memory” as first lecturer in this year’s IGERT Computational Neuroscience Seminar series. Sen, now Chief, Laboratory of Molecular Biology and Immunology, National Institute on Aging, will speak on Wednesday, Oct 5 at 4:00 pm in Gzang 121, on the subject of how “Loops within Loops Generate the Chromosome Conformation of the Immunoglobulin Heavy Chain Gene Locus”.

Ranjan Sen (left) and Xiao-Jing Wang (right), shown as they appeared in old Brandeis faculty webpages from days past.

For background on the subject of Ranjan’s talk, see The origins of NF-κB, published recently in Nature Immunology.

KC Hayes, obesity, and the Asian Food Network

BrandeisNOW has a new story about Professor KC Hayes, the Asian Food Network, the worldwide trend to greater obesity, and what should and shouldn’t be in your diet.

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