Biogenesis and topology of the transient receptor potential Ca2+ channel TRPC1.

The TRPC ion channels are candidates for the store-operated Ca(2+) entry pathway activated in response to depletion of intracellular Ca(2+) stores. Hydropathy analyses indicate that these proteins contain eight hydrophobic regions (HRs) that could potentially form alpha-helical membrane-spanning segments. Based on limited sequence similarities to other ion channels, it has been proposed that only six of the eight HRs actually span the membrane and that the last two membrane-spanning segments (HRs 6 and 8) border the ion-conducting pore of which HR 7 forms a part.

Involvement of phospholipase D in the cAMP-regulated exocytosis of rat parotid acinar cells.

The activation of beta-adrenergic receptors in rat parotid acinar cells causes intracellular cAMP elevation and appreciably stimulates the exocytotic release of amylase into saliva. The activation of Ca(2+)-mobilizing receptors also induces some exocytosis. We investigated the role of phospholipase D (PLD) in regulated exocytosis in rat parotid acinar cells.

Evidence that the transmembrane biogenesis of aquaporin 1 is cotranslational in intact mammalian cells.

Most polytopic membrane proteins are believed to integrate into the membrane of the endoplasmic reticulum (ER) cotranslationally. However, recent studies with Xenopus oocytes and dog pancreatic microsomes have suggested that this is not the case for human aquaporin 1 (AQP1). These experiments indicate that membrane-spanning segments (MSSs) 2 and 4 of AQP1 do not integrate into the membrane cotranslationally so that this protein initially adopts a four MSS topology.