Molecular aspects of fatty acid transport: mutations in the IYTSGTTGXPK motif impair fatty acid transport protein function

110

The fatty acid transport protein Fat1p functions as a component of the long-chain fatty acid transport apparatus in the yeast Saccharomyces cerevisiae. Fat1p has significant homologies to the mammalian fatty acid transport proteins (FATP) and the very long-chain acylCoA synthetases (VLACS). In order to further understand the functional roles intrinsic to Fat1p (fatty acid transport and VLACS activities), a series of 16 alleles carrying site-directed mutations within FAT1 were constructed and analyzed. Sites chosen for the construction of amino acid substitutions were based on conservation between Fat1p and the mammalian FATP orthologues and included the ATP/AMP and FATP/VLACS signature motifs. Centromeric and 2 plasmids encoding mutant forms of Fat1p were transformed into a yeast strain containing a deletion in FAT1 (fat1⌬). For selected subsets of FAT1 mutant alleles, we observed differences between the wild type and mutants in 1) growth rates when fatty acid synthase was inhibited with 45 M cerulenin in the presence of 100 M oleate (C 18:1 ), 2) levels of fatty acid import monitored using the accumulation of the fluorescent fatty acid 4,4-difluoro-5-methyl-4-bora3a,4a-diaza-S-indacene-3-dodecanoic acid and [ 3 H]oleate, 3) levels of lignoceryl (C 24:0 ) CoA synthetase activities, and 4) fatty acid profiles monitored using gas chromatography/mass spectrometry. In most cases, there was a correlation between growth on fatty acid/cerulenin plates, the levels of fatty acid accumulation, very long-chain fatty acyl-CoA synthetase activities, and the fatty acid profiles in the different FAT1 mutants. For several notable exceptions, the fatty acid transport and very long-chain fatty acyl-CoA synthetase activities were distinguishable. The characterization of these novel mutants provides a platform to more completely understand the role of Fat1p in the linkage between fatty acid import and activation to CoA thioesters.

Section: Discussionmentioning

confidence: 99%

Fatty Acid Transport in Saccharomyces cerevisiae

Zou

DiRusso

Čtrnáctá

et al. 2002

110

“…Studies from our laboratory (14,20) and others (4) have shown that single amino acid substitutions in the highly conserved IYTSGTTGXPK motif (amino acids 247-257) impair the function of FATP1 in fatty acid transport without altering its ability to be expressed or trafficked to the plasma membrane. This motif may play a role in binding ATP or in generation of an adenylated intermediate.…”

Section: Discussionmentioning

confidence: 99%

Oligomerization of the Murine Fatty Acid Transport Protein 1

Richards

Listenberger

Kelly

et al. 2003

The 63-kDa murine fatty acid transport protein 1 (FATP1) was cloned on the basis of its ability to augment fatty acid import when overexpressed in mammalian cells. The membrane topology of this integral plasma membrane protein does not resemble that of polytopic membrane transporters for other substrates. Western blot analysis of 3T3-L1 adipocytes that natively express FATP1 demonstrate a prominent 130-kDa species as well as the expected 63-kDa FATP1, suggesting that this protein may participate in a cell surface transport protein complex. To test whether FATP1 is capable of oligomerization, we expressed functional FATP1 molecules with different amino-or carboxyl-terminal epitope tags in fibroblasts. These epitope-tagged proteins also form apparent higher molecular weight species. We show that, when expressed in the same cells, differentially tagged FATP1 proteins co-immunoprecipitate. The region between amino acid residues 191 and 475 is sufficient for association of differentially tagged truncated FATP1 constructs. When wild type FATP1 and the non-functional s250a FATP1 mutant are co-expressed in COS7 cells, mutant FATP1 has dominant inhibitory function in fatty acid uptake assays. Taken together, these results are consistent with a model in which FATP1 homodimeric complexes play an important role in cellular fatty acid import.

“…To investigate the role of ACS activity in FATP4 in vivo, and to determine whether FATP4 might exhibit any function in the absence of ACS activity, we generated a Fatp4 cDNA (⌬Fatp4) carrying two amino acid substitutions, S247G and T249G. Altering these critical residues inhibits ACS activity (43,44) and blocks uptake of Bodipy B 12 -FA (Ref. 42 and personal observations).…”

Section: Molecular Analysis Of Ceramide Fatty Acid Composition-mentioning

confidence: 99%

Keratinocyte-specific Expression of Fatty Acid Transport Protein 4 Rescues the Wrinkle-free Phenotype in Slc27a4/Fatp4 Mutant Mice

Moulson

Lin

White

et al. 2007

FATP4 (fatty acid transport protein 4; also known as SLC27A4) is the most widely expressed member of a family of six long chain fatty acid transporters. FATP4 is highly expressed in enterocytes and has therefore been proposed to be a major importer of dietary fatty acids. Two independent mutations in Fatp4 cause mice to be born with thick, tight, shiny, "wrinklefree" skin and a defective skin barrier; they die within hours of birth from dehydration and restricted movements. In contrast, induced keratinocyte-specific deficiency of FATP4 in adult mice causes only mild skin abnormalities. Therefore, whether the loss of FATP4 from skin or a systemic gestational metabolic defect causes the severe skin defects and neonatal lethality remain important unanswered questions. To investigate the basis for the phenotype, we first generated wild-type tetraploid/mutant diploid aggregates that should lead to rescue of any abnormalities caused by loss of FATP4 from the placenta. However, the skin phenotype was not ameliorated. We then generated transgenic mice expressing exogenous FATP4 either widely or specifically in suprabasal keratinocytes, and we bred the transgenes onto the Fatp4 ؊/؊ background. Both modes of FATP4 expression led to rescue of the neonatally lethal skin defects, and the resulting mice were viable and fertile. Keratinocyte expression of an FATP4 variant with mutations in the acyl-CoA synthetase domain did not provide any degree of rescue. We conclude that expression of FATP4 with an intact acyl-CoA synthetase domain in suprabasal keratinocytes is necessary for normal skin development and that FATP4 functions in establishing the cornified envelope. Fatty acid transport proteins (FATPs)2 compose a family of transmembrane proteins that facilitate cellular long chain fatty acid uptake (1-3). The most widely expressed member of this family is FATP4 (4, 5), which is encoded by Slc27a4 (solute carrier family 27 member 4 gene). The most robust expression of FATP4 is in intestinal epithelial cells (5), but its broad expression pattern is suggestive of functions in many organs.Surprisingly, the "wrinkle-free" phenotype we discovered in mice with a spontaneous mutation in Slc27a4 (Slc27a4 wrfr ) and the identical phenotype of mice with a targeted Slc27a4 mutation (Slc27a4) indicate critical roles for FATP4 in skin and hair development (6, 7). For these mutations, which both affect exon 3, homozygotes are born with tight, thick, shiny skin and a defective skin barrier; they die shortly after birth because of restricted movements and dehydration. These defects are reminiscent of human restrictive dermopathy, but this disease has recently been linked to mutations in zinc metalloproteinase STE24 (8 -10). Interestingly, deletion of Slc27a4 exons 2 and 3 (the first two coding exons; Slc27a4 tm1Asta ) results in embryonic lethality prior to embryonic day 9.5 (11). The reason for the striking difference in phenotypes remains unknown, but it may involve a partially functional truncated protein in the first two mutants or early ...