Showing papers by "Thomas Martin published in 2009"
TL;DR: An unexpected activity of a priming protein to accelerate fusion by efficiently promoting trans-SNARE complex formation is revealed in a SNARE-dependent liposome fusion assay using VAMP2-containing donor and syntaxin-1/SNAP-25-containing acceptor liposomes.
Abstract: Ca2+-dependent activator protein for secretion (CAPS) is an essential factor for regulated vesicle exocytosis that functions in priming reactions before Ca2+-triggered fusion of vesicles with the plasma membrane. However, the precise events that CAPS regulates to promote vesicle fusion are unclear. In the current work, we reconstituted CAPS function in a SNARE-dependent liposome fusion assay using VAMP2-containing donor and syntaxin-1/SNAP-25-containing acceptor liposomes. The CAPS stimulation of fusion required PI(4,5)P2 in acceptor liposomes and was independent of Ca2+, but Ca2+ dependence was restored by inclusion of synaptotagmin. CAPS stimulated trans-SNARE complex formation concomitant with the stimulation of full membrane fusion at physiological SNARE densities. CAPS bound syntaxin-1, and CAPS truncations that competitively inhibited syntaxin-1 binding also inhibited CAPS-dependent fusion. The results revealed an unexpected activity of a priming protein to accelerate fusion by efficiently promoting trans-SNARE complex formation. CAPS may function in priming by organizing SNARE complexes on the plasma membrane.
71 citations
TL;DR: The slow evoked release of neuropeptides could be attributed to very prolonged latencies from stimulation to fusion and transient fusion-pore openings that might limit cargo secretion.
Abstract: Evoked neuropeptide secretion in the central nervous system occurs slowly, but the basis for slow release is not fully understood. Whereas exocytosis of single synaptic vesicles in neurons and of dense-core vesicles (DCVs) in endocrine cells have been directly visualized, single DCV exocytic events in neurons of the central nervous system have not been previously studied. We imaged DCV exocytosis in primary cultured hippocampal neurons using fluorescent propeptide cargo and total internal reflectance fluorescence microscopy. The majority of Ca2+-triggered exocytic events occurred from immobile plasma-membrane-proximal DCVs in the cell soma, whereas there were few events in the neurites. Strikingly, DCVs in the cell soma exhibited 50-fold greater release probabilities than those in neurites. Latencies to depolarization-evoked fusion for DCVs were surprisingly long, occurring with an average time constant (τ) of 16 seconds for DCVs in the soma and even longer for DCVs in neurites. All of the single DCV release events exhibited rapid fusion-pore openings and closures, the kinetics of which were highly dependent upon Ca2+ levels. These `kiss-and-run' events were associated with limited cargo secretion. Thus, the slow evoked release of neuropeptides could be attributed to very prolonged latencies from stimulation to fusion and transient fusion-pore openings that might limit cargo secretion.
62 citations
TL;DR: Perifosine in combination with Vel (+/− dex) has been generally well tolerated and continues to demonstrate impressive activity in both heavily pre-treated, Vel-refractory pts, with an ORR of 38% and OS of 16 mos, and in Vel-relapsed pts with an OrR of 55%, a median TTP of 8.4 mos.
16 citations
TL;DR: The results identify a functionally important N-terminal phosphorylation site that regulates CAPS activity in priming vesicle exocytosis and CK2 is the likely in vivo CAPS protein kinase based on inhibition of phosphorylated by tetrabromo-2-benzotriazole in PC12 cells and by the identity of in vivo and in vitro phosphorylations sites.
15 citations
TL;DR: CFZ can be administered to MM pts with substantial renal dysfunction and does not require dose adjustment, and Responses in relapsed and refractory MM ptsWith renal insufficiency are encouraging, and further evaluation of CFZ in renally impaired patients is ongoing.
13 citations
1 citations