Abstract The cell-type restricted expression of cyto- plasmic microvesicle membrane protein isoforms may be a consequence of the functional adaptation of these vesi- cles to the execution of specialized processes in cells of different specialization. To characterize the expression of the vesicle protein pantophysin, an isoform of the synap- tic vesicle proteins synaptophysin and synaptoporin, we have prepared and characterized antibodies useful for the immunological detection of pantophysin in vitro and in situ. Using these reagents, we show by immunoblot ana- lyses that pantophysin expression is not homogeneous but differs significantly between various bovine tissues. Furthermore, these differences are not exactly paralleled by the expression of other vesicle proteins of the SCAMP (secretory carrier-associated membrane protein) and VAMP (vesicle-associated membrane protein) types that have previously been localized to pantophysin vesi- cles in cultured cells. By immunofluorescence microsco- py, pantophysin expression is seen predominantly in non-neuroendocrine cells with pronounced membrane traffic. Pantophysin staining codistributes with SCAMP and VAMP immunoreactivities in most instances but dif- fers in some. Remarkably, pantophysin staining in liver is restricted to cells surrounding sinusoids and is not de- tectable in hepatocytes, similar to that of the SCAMP and VAMP isoforms as detected by our reagents in tissue sections. Key words Vesicle protein · Physin · Secretory carrier-associated membrane protein · Vesicle-associated membrane protein · Synaptobrevin · Expression · Liver · Bovine · Human Introduction Research over the last few years has revealed that basic molecular mechanisms are shared during the regulation of vesicle formation and fusion in many different path- ways of membrane trafficking in diverse cells (for re- views, see Ferro-Novick and Jahn 1994; Rothman 1994; Pfeffer 1996). Especially intriguing are the remarkable similarities between the highly specialized secretory transmitter-containing vesicles in neurons and constitu- tive vesicles participating in the ubiquitous house-keep- ing functions of intracellular membrane movement in all eukaryotic cells (for reviews, see Bennett and Scheller 1993; Ferro-Novick and Jahn 1994; Rothman 1994; Süd- hof 1995; Calakos and Scheller 1996; Linial and Parnas 1996). These similarities are reflected by the presence, in constitutive vesicles, of molecules that share significant sequence features with specific synaptic vesicle proteins (Simons and Zerial 1993; McMahon et al. 1993; Haass et al. 1996; Südhof and Rizo 1996; Advani et al. 1998; Gal- li et al. 1998; Janz and Südhof 1998; Shimuta et al. 1998; Takeshima et al. 1998; Wong et al. 1998). The characterization of the expression patterns of individual members of these polypeptide groups may therefore help to elucidate their functions in a given cellular context. A particularly abundant type of integral membrane protein of synaptic vesicles is characterized by four transmembrane domains and cytoplasmic ends. Three distinct gene families encoding such polypeptides have been identified to date: (1) a group that we shall refer to as physins, encompassing the two neuronal isoforms synaptophysin and synaptoporin (also termed syn- This work was supported by the German Research Council (Le566/3–1) R. Windoffer · M. Borchert-Stuhlträger · S. Thomas R.E. Leube ( ✉ ) Department of Anatomy, Johannes Gutenberg-University Mainz, Becherweg 13, D-55099 Mainz, Germany e-mail: leube@mail.uni-mainz.de; Tel.: +49 6131 392731; Fax: +49 6131 394615 N.K. Haass · M. Hergt Division of Cell Biology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany C.J. Bulitta Klinik für Allgemein- und Abdominalchirurgie, Universitätsklinik Mainz, Langenbeckstraße 1, D-55101 Mainz, Germany Cell Tissue Res (1999) 296:499–510 © Springer-Verlag 1999 REGULAR ARTICLE Reinhard Windoffer · Monika Borchert-Stuhlträger Nikolas K. Haass · Sabine Thomas · Michaela Hergt Clemens J. Bulitta · Rudolf E. Leube Tissue expression of the vesicle protein pantophysin Received: 20 October 1998 / Accepted: 8 January 1999