Fig. 1. Expression of small GTPase Rab27 and its effectors (Slp and Slac2) in rat parotid glands. (A) Expression of the Slp and Slac2 family members in rat parotid glands. Similar amounts of recombinant T7-tagged Slp1-5 and Slac2-a/b/c expressed in COS-7 cells (lane 1; see B) and total homogenates of rat parotid glands (50 µg; lane 2) were loaded on 7.5% SDS-PAGE and immunoblotted with anti-Slp1, anti-Slp2-a, anti-Slp3-a, anti-Slp4-a, anti-Slp5, anti-Slac2-a, anti-Slac2-b, or anti-Slac2-c specific antibody. Note that the Slp4-a and Slac2-c proteins, but not the other Rab27 effectors, were easily detected in rat parotid glands (arrowheads). The asterisk indicates non-specific interaction of the anti-Slac2-a antibody. (B) Recombinant T7-Slp1-5 and T7-Slac2-a/b/c were used as positive controls in A. Similar amounts of the T7-tagged proteins except for T7-Slac2-b were loaded into each lane. The positions of the molecular mass markers (in kDa) are shown on the left. (C) Expression of Rab27A and Rab27B in rat parotid glands. The same amounts of FLAG-tagged Rab27A (lane 1) and Rab27B (lane 2), and total homogenates of rat parotid glands (50 µg; lane 3) were loaded on 12.5% SDS-PAGE and immunoblotted with anti-Rab27A (top panel), anti-Rab27B (middle panel), or anti-FLAG tag antibody (bottom panel). Judging from the intensity of the Rab27A and Rab27B bands calibrated with the FLAG-tagged recombinant proteins, expression of Rab27B was dominant in parotid glands. Under our experimental conditions, Rab27A, Rab27B, Slp4-a, and Slac2-c were detected as single immunoreactive bands.