Evaluation of the role of the Endoplasmic Reticulum-Golgi transit in the biogenesis of peroxisomal membrane proteins in wild type and peroxisome biogenesis mutant CHO cells

• Main Authors: ANDRÉS TORO, CRISTIAN ARREDONDO, GONZALO CORDOVA, CLAUDIA ARAYA, JOSÉ L PALACIOS, ALEJANDRO VENEGAS, MASASHI MORITA, TSUNEO IMANAKA, MANUEL J SANTOS
• Format: Article
• Language: English
• Published: BMC 2007-01-01
• Series: Biological Research
• Subjects: adrenoleukodystrophy; ALDRP; endoplasmic reticulum; peroxisome biogenesis; Pex3p and PMP70
• Online Access: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000200014

Peroxisomes are thought to be formed by division of pre-existing peroxisomes after the import of newly synthesized proteins. However, it has been recently suggested that the endoplasmic reticulum (ER) provides an alternative de novo mechanism for peroxisome biogenesis in some cells. To test a possible role of the ER-Golgi transit in peroxisome biogenesis in mammalian cells, we evaluated the biogenesis of three peroxisomal membrane proteins (PMPs): ALDRP (adrenoleukodystrophy related protein), PMP70 and Pex3p in CHO cells. We constructed chimeric genes encoding these PMPs and green fluorescent protein (GFP), and transiently transfected them to wild type and mutant CHO cells, in which normal peroxisomes were replaced by peroxisomal membrane ghosts. The expressed proteins were targeted to peroxisomes and peroxisomal ghosts correctly in the presence or absence of Brefeldin A (BFA), a drug known to block the ER-Golgi transit. Furthermore, low temperature did not disturb the targeting of Pex3p-GFP to peroxisomes. We also constructed two chimeric proteins of PMPs containing an ER retention signal "DEKKMP": GFP-ALDRP-DEKKMP and myc- Pex3p-DEKKMP. These proteins were mostly targeted to peroxisomes. No colocalization with an ER maker was found. These results suggest that the classical ER-Golgi pathway does not play a major role in the biogenesis of mammalian PMPs