Skip to main content
. Author manuscript; available in PMC: 2008 Aug 8.
Published in final edited form as: Biochemistry. 2008 May 17;47(23):6138–6147. doi: 10.1021/bi800182t

FIGURE 5.

FIGURE 5

SPTLC1 blocks the exit of ABCA1 from the ER. (A) SPTLC1 traps ABCA1 in the ER as evidenced by the strong colocalization of GFP-ABCA1 with a DsRed fusion protein carrying the calreticulin KDEL ER targeting sequence when expressed in the presence of SPTLC1 (bottom panels). GFP-ABCA1 expressed alone does not colocalize with the DsRed ER signal (top panels). (B) As expected, immunofluorescent localization of HA-tagged SPTLC1 showed it also colocalized with the DsRed ER protein (top panels) and with the trapped GFP-ABCA1 (bottom panels). (C) SPTLC1 expression does not alter the localization of the sodium phosphate transporter as indicated by the lack of colocalization of a GFP-NaPi transporter with HA-SPTLC1. (D) Sucrose gradient fractionation confirms SPTLC1 altered the distribution of ABCA1 in 293ET cells such that a greater percent of ABCA1 cofractionates with SPTLC1 in the ER. Immunoblots of the distribution of ABCA1 and SPTLC1 across the gradient are shown, and graphed is the percent distribution of ABCA1 and SPTLC1 in each fraction.