An isoform of the giant protein titin is a master regulator of human T lymphocyte trafficking

Response to multiple microenvironmental cues and resilience to mechanical stress are essential features of trafficking leukocytes. Here, we describe unexpected role of titin (TTN), the largest protein encoded by the human genome, in the regulation of mechanisms of lymphocyte trafficking. Human T and B lymphocytes ex-press five TTN isoforms, exhibiting cell-specific expression, distinct localization to plasma membrane micro -domains, and different distribution to cytosolic versus nuclear compartments. In T lymphocytes, the LTTN1 isoform governs the morphogenesis of plasma membrane microvilli independently of ERM protein phosphor-ylation status, thus allowing selectin-mediated capturing and rolling adhesions. Likewise, LTTN1 controls chemokine-triggered integrin activation. Accordingly, LTTN1 mediates rho and rap small GTPases activation, but not actin polymerization. In contrast, chemotaxis is facilitated by LTTN1 degradation. Finally, LTTN1 con-trols resilience to passive cell deformation and ensures T lymphocyte survival in the blood stream. LTTN1 is, thus, a critical and versatile housekeeping regulator of T lymphocyte trafficking

An isoform of the giant protein titin is a master regulator of human T lymphocyte trafficking

Response to multiple microenvironmental cues and resilience to mechanical stress are essential features of trafficking leukocytes. Here, we describe unexpected role of titin (TTN), the largest protein encoded by the human genome, in the regulation of mechanisms of lymphocyte trafficking. Human T and B lymphocytes express five TTN isoforms, exhibiting cell-specific expression, distinct localization to plasma membrane microdomains, and different distribution to cytosolic versus nuclear compartments. In T lymphocytes, the LTTN1 isoform governs the morphogenesis of plasma membrane microvilli independently of ERM protein phosphorylation status, thus allowing selectin-mediated capturing and rolling adhesions. Likewise, LTTN1 controls chemokine-triggered integrin activation. Accordingly, LTTN1 mediates rho and rap small GTPases activation, but not actin polymerization. In contrast, chemotaxis is facilitated by LTTN1 degradation. Finally, LTTN1 controls resilience to passive cell deformation and ensures T lymphocyte survival in the blood stream. LTTN1 is, thus, a critical and versatile housekeeping regulator of T lymphocyte trafficking

Solution to nascent hyrdogen challenge

NRC publication: Ye

Mass spectrometric separation and quantitation of overlapping isotopologues. H2O/HOD/D2O and H2Se/HDSe/D2Se mixtures

NRC publication: Ye

Determination of S-nitrosoglutathione and other nitrosothiols by p-hydroxymercurybenzoate derivatization and reverse phase chromatography coupled with chemical vapor generation atomic fluorescence detection

NRC publication: Ye

The mechanism of formation of volatile hydrides by tetrahydroborate (III) derivatization: a mass spectrometric study performed with deuterium labeled reagents

In order to clarify the mechanism of hydride formation, the isotopic composition of arsine, stibine, bismuthine, germane, stannane and hydrogen selenide formed by derivatization with either NaBD4 (TDB) or NaBH4 (THB) with inorganic As(III), Sb(III), Bi(III), Ge(IV), Sn(IV) and Se(IV) in aqueous reaction media and under various reaction conditions was determined. Batch hydride generation and gas chromatography\u2013mass spectrometry (GC\u2013MS) were employed. The analyte, present in 0.5\u20135 ml of acid solution (0.1\u201310 M in HCl or HNO3 or HClO4) was derivatized with 1 ml of 0.25\u20130.5 M TDB / THB in 0.1 M NaOH solution. For TDB derivatization in H2O reaction media, almost pure BiD3 and SbD3 were always obtained for Bi(III) and Sb(III). Nearly pure AsD3 could be obtained only under some reaction conditions. In general, for As(III), the isotopic composition of the arsines depends strongly on reaction conditions and included all possible AsHnD3 12n from almost pure AsD3 to almost pure AsH3. For Ge(IV) and Sn(IV), the isotopic composition of generated GeHnD4 12n and SnHnD4 12n depends on reaction conditions, but pure GeD4 and SnD4 could never be obtained. Pure H2Se was obtained in all cases, independent of reaction conditions. The occurrence of side reactions involving D\u2013H exchange in TBD during its hydrolysis and before the derivatization step, as well as on recently formed hydrides following derivatization was investigated. D\u2013H exchange in TDB during acid hydrolysis appears to occur to a limited extent. Amongst the hydrides, H2Se undergoes H\u2013D exchange whereas germane and stannane do not exchange at all. Arsine undergoes D\u2013H exchange at elevated acidities (pH < 0) whereas stibine and bismuthine do not exchange significantly during the generation and stripping steps. A reaction model for hydride generation is proposed accounting for primary reactions giving rise to hydride formation through reaction intermediates, as well as side reactions involving D\u2013H exchange and decomposition of reactive hydroboron species, reaction intermediates and final products. Hydrides are formed by direct hydrogen transfer from boron to the analyte atom, most likely through concerted mechanisms taking place via reaction intermediates.NRC publication: Ye

Mass spectrometric separation and quantitation of overlapping isotopologues. Deuterium containing hydrides of As, Sb, Bi, Sn, and Ge

NRC publication: Ye

Mechanism of generation of volatile hydrides of trace elements by aqueous tetrahydroborate(III). Mass spectrometric studies on reaction products and intermediates

The mechanism of generation of volatile metal/metalloid hydrides by derivatization with borane complexes is presented. This reaction has been employed for ultratrace element analysis since 1972 and has been the source of much controversy in regard to the reaction mechanism. Here we investigated this derivatization by using As(III), Sb(III), Bi(III), MeAsO(OH)2, and Me2AsO(OH) as model analytes and NaBH4, NaBD4, tert-BuNH2BH3, and Me2NHBH3 as borane reagents. The identification of reaction products and intermediates observed under various reaction conditions was performed by gas chromatography/mass spectrometry and electrospray ionization mass spectrometry. An alternative reaction model, based on the formation of analyte 12borane complex (ABC) intermediates, is able to reconcile all the experimental evidence reported in the literature. In this study, we provide definitive evidence of the ABC hydride generation mechanism, which shows that the generation of volatile hydrides occurs via formation of ABC intermediates between hydroboron species and the analyte substrate followed by the direct transfer of hydrogen from boron to the analyte atom, and fast hydrolysis leading to the final product.Peer reviewed: YesNRC publication: Ye