STIM1 is a MT-plus-end-tracking protein involved in remodeling of the ER

I Grigoriev, S Gouveia, Babet Vaart, Jeroen Demmers, JT Smyth, S Honnappa, EC Splinter, MO Steinmetz, JW Putney, CC Hoogenraad, Anna Akhmanova

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Abstract

Stromal interaction molecule 1 (STIM1) is a transmembrane protein that is essential for store-operated Ca2+ entry, a process of extracellular Ca2+ influx in response to the depletion of Ca2+ stores in the endoplasmic reticulum (ER) (reviewed in [1-4]). STIM1 localizes predominantly to the ER; upon Ca2+ release from the ER, STIM1 translocates to the ER-plasma membrane junctions and activates Ca2+ channels (reviewed in [1-4]). Here, we show that STIM1 directly binds to the microtubule-plus-end-tracking protein EB1 and forms EB1-dependent comet-like accumulations at the sites where polymerizing microtubule ends come in contact with the ER network. Therefore, the previously observed tubulovesicular motility of GFP-STIM1 [5] is not a motor-based movement but a traveling wave of diffusion-dependent STIM1 concentration in the ER membrane. STIM1 overexpression strongly stimulates ER extension occurring through the microtubule "tip attachment complex" (TAC) mechanism [6, 7], a process whereby an ER tubule attaches to and elongates together with the EB1-positive end of a growing microtubule. Depletion of STIM1 and EB1 decreases TAC-dependent ER protrusion, indicating that microtubule growth-dependent concentration of STIM1 in the ER membrane plays a role in ER remodeling.
Original languageUndefined/Unknown
Pages (from-to)177-182
Number of pages6
JournalCurrent Biology
Volume18
Issue number3
DOIs
Publication statusPublished - 2008

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