Growing evidence suggests that phosphoinositides play an important role in membrane traffic. A polyphosphoinositide phosphatase, synaptojanin 1, was identified as a major presynaptic protein associated with endocytic coated intermediates. We report here that synaptojanin 1-deficient mice exhibit neurological defects and die shortly after birth. In neurons of mutant animals, PI(4,5)P2 levels are increased, and clathrin-coated vesicles accumulate in the cytomatrix-rich area that surrounds the synaptic vesicle cluster in nerve endings. In cell-free assays, reduced phosphoinositide phosphatase activity correlated with increased association of clathrin coats with liposomes. Intracellular recording in hippocampal slices revealed enhanced synaptic depression during prolonged high-frequency stimulation followed by delayed recovery. These results provide genetic evidence for a crucial role of phosphoinositide metabolism in synaptic vesicle recycling.

ImagingAll patients underwent 2.5-mm axial NECT and CECT as well as a CTA (acquired at 0.625 mm and reformatted into 1.25 mm). Two authors (P.M. and S.W.H.) retrospectively evaluated NECTs for presence of large vessel thrombus. A region of interest was drawn Background and Purpose-Can lysability of large vessel thrombi in acute ischemic stroke be predicted by measuring clot density on admission nonenhanced CT (NECT), postcontrast enhanced CT, or CT angiogram (CTA)? Methods-We retrospectively studied 90 patients with acute large vessel ischemic strokes treated with intravenous (IV) tPA, intra-arterial (IA) tPA, and/or mechanical thrombectomy devices.

Synaptojanin 1 is a polyphosphoinositide phosphatase implicated in synaptic vesicle recycling. We used FM1-43 imaging and electron microscopy in cultured cortical neurons from control and synaptojanin 1 knockout mice to study how the absence of this protein affects specific steps of the synaptic vesicle cycle. Exo͞endocytosis after a moderate stimulus was unchanged. However, during prolonged stimulation, the regeneration of fusion-competent synaptic vesicles was severely impaired. In stimulated nerve terminals, there was a persistent accumulation of clathrin-coated vesicles and a backup of newly reformed vesicles in the cytomatrix-rich area around the synaptic vesicle cluster. These findings demonstrate that synaptojanin 1 function is needed for the progression of recycling vesicles to the functional synaptic vesicle pool. N eurotransmission and its reliability depend on the efficient and precise recycling of synaptic vesicles in the presynaptic nerve terminal (1, 2). Vesicle fusion and neurotransmitter release are followed by rapid retrieval and repackaging of synaptic vesicle membrane components into new functional vesicles. Morphologic, biochemical, genetic, and functional evidence points to an important role of the clathrin-mediated recycling pathway in this process (1,(3)(4)(5). Alternative and parallel pathways may also participate in recycling (1, 2, 6-9).Growing evidence suggests that phosphoinositides play an important role in the synaptic vesicle cycle via their interaction with endocytic and actin regulatory proteins (10-13). Phosphoinositides, PI(4,5)P 2 in particular, bind clathrin adaptors such as AP-2 (14-16), AP180 (17,18), and epsin (19,20), as well as the GTPase dynamin (21, 22), which is critically required for the fission of endocytic vesicles (23, 24). They also regulate a variety of proteins that control actin nucleation (13,25,26). Actin, in turn, is thought to play an important role in clathrin-mediated recycling by generating and organizing cytoskeletal scaffolds at endocytic zones (27-29) and, possibly, by contributing to the translocation of newly formed endocytic vesicles to the synaptic vesicle cluster (30-34).Synaptojanin 1 is a polyphosphoinositide phosphatase highly enriched in presynaptic nerve terminals and localized to recycling intermediates in synaptosomes (35,36). Its COOHterminal proline-rich domain interacts with several accessory factors implicated in synaptic vesicle recycling, including amphiphysin (35), endophilin (37), (38), intersectin (34, 39), and syndapin͞pacsin (40, 41). Its NH 2 -terminal Sac1-like module hydrolyzes the phosphates of PI(3)P, PI(4)P, and PI(3,5)P 2 (42), whereas its central phosphatase module hydrolyzes the 5Ј phosphate of PI(4,5)P 2 and PI(3,4,5)P 3 (43,44). By means of these enzymatic activities, synaptojanin can dephosphorylate polyphosphoinositides to phosphatidylinositol and thereby function as a negative regulator of the interactions between membranes, coat proteins, and regulatory factors for actin.In mice knockout studies, the absence of ...