Madhu Mahankali

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MTLn3 cells are highly invasive breast adenoacarcinoma cells. The relative level of the epidermal-growth-factor-stimulated invasion of this cell line is greater than two other breast cancer cell lines (MDA-MB-231 and MCF-7) and one non-small cell lung cancer cell line (H1299). We have determined that the mechanism of cancer cell invasion involves the(More)
We have discovered that the enzyme phospholipase D2 (PLD2) binds directly to the small GTPase Rac2, resulting in PLD2 functioning as a guanine nucleotide exchange factor (GEF), because it switches Rac2 from the GDP-bound to the GTP-bound states. This effect is large enough to be meaningful (∼72% decrease for GDP dissociation and 300% increase for GTP(More)
We report the novel finding that Phospholipase D2 (PLD2), through its PX and PH domains, binds specifically to Ras and catalyzes the GDP/GTP exchange (i.e., is a GEF), with potency comparable to Ras-GRF-1, a known Ras-GEF. Cells overexpressing PLD2-GEF inactive mutants (F129Y and R172C/L173A) fail to stimulate cell proliferation compared to the wild(More)
We document a biphasic effect of Rac2 on the activation and inhibition of PLD2. Cells overexpressing Rac2 and PLD2 simultaneously show a robust initial (<10 min) response toward a chemoattractant that is later (>30 min) greatly diminished over PLD2-only controls. The first phase is due to the presence of a Rac2-PLD2 positive-feedback loop. To explain the(More)
Phagocytosis is a primary innate response of both macrophages and neutrophils involving the formation of filamentous actin (F-actin)-rich protrusions that are extended around opsonized pathogens to form a phagocytic cup, resulting in their subsequent internalization. The molecular mechanism for this is still not completely understood. We now show for the(More)
Phospholipase D (PLD) and small GTPases are vital to cell signaling. We report that the Rac2 and the PLD2 isoforms exist in the cell as a lipase-GTPase complex that enables the two proteins to elicit their respective functionalities. A strong association between the two molecules was demonstrated by co-immunoprecipitation and was confirmed in living cells(More)
Membrane ruffling is the formation of actin rich membrane protrusions, essential for cell motility. The exact mechanism of ruffling is not fully known. Using YFP and CFP fluorescent chimeras, we show for the first time a co-localization of Phospholipase D2 (PLD2) and Growth factor Receptor Bound protein-2 (Grb2) with actin-rich membrane protrusions of(More)
Timely activation of Aurora kinase A (AURA, also known as AURKA) is vital for centrosome formation and the progression of mitosis. Nonetheless, it is still unclear if and when other cellular functions are activated by AURA. We report here that Src phosphorylates and activates AURA at T288, and AURA also activates focal adhesion kinase (FAK, also known as(More)
We have demonstrated that phospholipase D2 (PLD2) is a guanine nucleotide exchange factor (GEF) for Rac2 and determined the PLD2 domains and amino acid site(s) responsible for its GEF activity. Experiments using GST fusion proteins or GST-free counterparts, purified proteins revealed that the PX domain is sufficient to exert GEF activity similar to(More)
Monocytes and neutrophils infiltrate into tissues during inflammation and stay for extended periods of time until the initial insult is resolved or sometimes remain even longer in the case of chronic inflammation. The mechanism as to why phagocytes become immobilized after the initial cell migration event is not understood completely. Here, we show that(More)