Identification of a novel sodium-dependent fructose transport activity in the hepatopancreas of the Atlantic lobsterHomarus americanus

Transepitheliald-glucose andd-fructose transport across the American lobster,Homarus americanus, intestine

“…In contrast, epithelial transport of D-fructose by both invertebrate epithelial cells significantly departed from the mammalian paradigm by displaying sodium-dependent transport at both cell poles that was unaffected by a 10-fold excess concentration of D-glucose. As discussed in Sterling and Ahearn's paper (Sterling and Ahearn, 2011), BLAST sequence alignments of horseshoe crab cDNA with mouse SGLT4 protein sequence and lobster sequence alignments with human SGLT4 protein sequence (Sterling et al, 2009) suggested the high probability of orthologs of this sodium-dependent mammalian D-fructose transporter (Tazawa et al, 2005) being present in both invertebrates. Sodium-dependent D-glucose and D-fructose transport in the same digestive tract epithelium is a significant departure from the sugar transport properties characterized in many vertebrate and invertebrate species, suggesting a potentially more diverse arrangement of sugar transport proteins at sites of nutrient absorption than strictly defined by the mammalian paradigm.…”

“…Two studies involving marine invertebrates, of considerably different phylogenetic histories, were recently carried out to investigate epithelial sugar transport processes of their respective digestive tracts (Sterling et al, 2009;Sterling and Ahearn, 2011). These studies used a combination of isolated hepatopancreatic cell suspensions and purified membrane vesicles of epithelial brush border and basolateral membranes of the 'living fossil' Limulus polyphemus (horseshoe crab) and H. americanus to define the nature of sugar transport in similar gastrointestinal organs from arthropod species evolutionarily separated from each other by at least 250 million years.…”

“…In crustaceans, the hepatopancreas and the intestine play a role in the absorption of dietary glucose (Ahearn et al, 1985;Verri et al, 2001), with the hepatopancreas being the major site of sugar absorption (Ahearn and Maginniss, 1977;Chu, 1986;Sterling et al, 2009). The crustacean hepatopancreas is a large, bilateral organ that is composed of five different cell types: E, F, R, B and M cells (Verri et al, 2001).…”

“…In contrast, the intestine is made up of a single type of epithelial cell and is considered a scavenger organ that absorbs nutrients that were not taken up by the hepatopancreas (Ahearn et al, 1992a;Wright and Ahearn, 1997). The mechanism of glucose transport in purified brush boarder membrane vesicles of hepatopancreatic epithelial cells in shrimp (Panaeus japonicas) and lobster (Homarus americanus) is carrier mediated via an SGLT1-like transport protein (Ahearn et al, 1985;Verri et al, 2001;Sterling et al, 2009). …”

Glucose and other hexoses transporters in marine invertebrates: A mini review

“…Some of these transporters are also found in invertebrate species including insects (Caccia et al 2007); snails (Barber et al 1985); shrimp (Blaya et al 1998;Verri et al 2001;Vilella et al 2003), lobsters (Ahearn et al 1985;Verri et al 2001;Mandal et al 2003;Sterling et al 2009); horseshoe crab Ahearn, 2011), mussel (Louzao et al 1993) and oyster (Hanquet et al 2011). In particular, in the oysters a SGLT homolog has been sequenced (Huvet et al 2004).…”