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Pedram Lab / Publications
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14 Publications

Showing 11-14 of 14 results
09/12/18 | A bulky glycocalyx fosters metastasis formation by promoting G1 cell cycle progression
Woods EC, Kai F, Barnes JM, Pedram K, Pickup MW, Hollander MJ, Weaver VM, Bertozzi CR
eLife. Sep-12-2018;6:. doi:

Metastasis depends upon cancer cell growth and survival within the metastatic niche. Tumors which remodel their glycocalyces, by overexpressing bulky glycoproteins like mucins, exhibit a higher predisposition to metastasize, but the role of mucins in oncogenesis remains poorly understood. Here we report that a bulky glycocalyx promotes the expansion of disseminated tumor cells in vivo by fostering integrin adhesion assembly to permit G1 cell cycle progression. We engineered tumor cells to display glycocalyces of various thicknesses by coating them with synthetic mucin-mimetic glycopolymers. Cells adorned with longer glycopolymers showed increased metastatic potential, enhanced cell cycle progression, and greater levels of integrin-FAK mechanosignaling and Akt signaling in a syngeneic mouse model of metastasis. These effects were mirrored by expression of the ectodomain of cancer-associated mucin MUC1. These findings functionally link mucinous proteins with tumor aggression, and offer a new view of the cancer glycocalyx as a major driver of disease progression.

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01/12/17 | Antibodies to biotin enable large-scale detection of biotinylation sites on proteins
Udeshi ND, Pedram K, Svinkina T, Fereshetian S, Myers SA, Aygun O, Krug K, Clauser K, Ryan D, Ast T, Mootha VK, Ting AY, Carr SA
Nature Methods. Jan-12-2017;14(12):1167 - 1170. doi: 10.1038/nmeth.4465

Although purification of biotinylated molecules is highly efficient, identifying specific sites of biotinylation remains challenging. We show that anti-biotin antibodies enable unprecedented enrichment of biotinylated peptides from complex peptide mixtures. Live-cell proximity labeling using APEX peroxidase followed by anti-biotin enrichment and mass spectrometry yielded over 1,600 biotinylation sites on hundreds of proteins, an increase of more than 30-fold in the number of biotinylation sites identified compared to streptavidin-based enrichment of proteins.

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01/03/16 | Spatially resolved proteomic mapping in living cells with the engineered peroxidase APEX2
Hung V, Udeshi ND, Lam SS, Loh KH, Cox KJ, Pedram K, Carr SA, Ting AY
Nature Protocols. Jan-03-2016;11(3):456 - 475. doi: 10.1038/nprot.2016.018

This protocol describes a method to obtain spatially resolved proteomic maps of specific compartments within living mammalian cells. An engineered peroxidase, APEX2, is genetically targeted to a cellular region of interest. Upon the addition of hydrogen peroxide for 1 min to cells preloaded with a biotin-phenol substrate, APEX2 generates biotin-phenoxyl radicals that covalently tag proximal endogenous proteins. Cells are then lysed, and biotinylated proteins are enriched with streptavidin beads and identified by mass spectrometry. We describe the generation of an appropriate APEX2 fusion construct, proteomic sample preparation, and mass spectrometric data acquisition and analysis. A two-state stable isotope labeling by amino acids in cell culture (SILAC) protocol is used for proteomic mapping of membrane-enclosed cellular compartments from which APEX2-generated biotin-phenoxyl radicals cannot escape. For mapping of open cellular regions, we instead use a 'ratiometric' three-state SILAC protocol for high spatial specificity. Isotopic labeling of proteins takes 5–7 cell doublings. Generation of the biotinylated proteomic sample takes 1 d, acquiring the mass spectrometric data takes 2–5 d and analysis of the data to obtain the final proteomic list takes 1 week.

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08/14/12 | Pediatric epilepsy surgery: long-term 5-year seizure remission and medication use
Hauptman JS, Pedram K, Sison CA, Sankar R, Salamon N, Vinters HV, Mathern GW
Neurosurgery. Feb-08-2013;71(5):985 - 993. doi: 10.1227/NEU.0b013e31826cdd5a

Background: It is unclear whether long-term seizure outcomes in children are similar to those in adult epilepsy surgery patients.

Objective: To determine 5-year outcomes and antiepilepsy drug (AED) use in pediatric epilepsy surgery patients from a single institution.

Methods: The cohort consisted of children younger than 18 years of age whose 5-year outcome data would have been available by 2010. Comparisons were made between patients with and without 5-year data (n = 338), patients with 5-year data for seizure outcome (n = 257), and seizure-free patients on and off AEDs (n = 137).

Results: Five-year data were available from 76% of patients. More seizure-free patients with focal resections for hippocampal sclerosis and tumors lacked 5-year data compared with other cases. Of those with 5-year data, 53% were continuously seizure free, 18% had late seizure recurrence, 3% became seizure free after initial failure, and 25% were never seizure free. Patients were more likely to be continuously seizure free if their surgery was performed during the period 2001 to 2005 (68%) compared with surgery performed from 1996 to 2000 (61%), 1991 to 1995 (36%), and 1986 to 1990 (46%). More patients had 1 or fewer seizures per month in the late seizure recurrence (47%) compared with the not seizure-free group (20%). Four late deaths occurred in the not seizure-free group compared with 1 in the seizure-free group. Of patients who were continuously seizure free, 55% were not taking AEDs, and more cortical dysplasia patients (74%) had stopped taking AEDs compared with hemimegalencephaly patients (18%).

Conclusion: In children, 5-year outcomes improved over 20 years of clinical experience. Our results are similar to those of adult epilepsy surgery patients despite mostly extratemporal and hemispheric operations for diverse developmental etiologies.

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