RESEARCH PROFILE

Our main interest is the study of the intracellular targeting of proteins in the plant secretory pathway.

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Most plant proteins of interest for human and animal nutrition, or of biotechnological value are located in, or travel through, the secretory pathway. After synthesis, secretory proteins are translocated into the endoplasmic reticulum (ER), where they acquire their mature tertiary and quaternary structure. They are then transported along the secretory system to their final destinations: the ER itself, the Golgi complex, the 'endosomes', the vacuoles, the plasma membrane or the extracellular space. Our research group is interested in three major processes that regulate the plant secretory system:
Sorting of proteins to plant storage vacuoles: We have isolated two novel vacuolar sorting signals (from ricin and phaseolin) and are now analysing their ability to interact with vacuolar sorting receptors. We use a combination of biochemistry, genetics and live confocal microscopy. We have recently generated a panel of fluorescent reporter proteins targeted to the vacuolar lumen or the vacuolar membrane. These are being used to study vacuolar biogenesis and targeting in developing Arabidopsis seeds. As part of the EU 'Pharma-Planta' consortium, we are also studying the intracellular targeting and fate of recombinant protein of medical importance, in particular monoclonal antibodies and HIV antigens.
ER quality control and protein degradation: how does the endoplasmic reticulum dispose of proteins that fail to fold or assemble correctly? Where does degradation occur? Which molecular chaperones are involved in the degradative process? How does the plant ER handle the synthesis of heterologous proteins with complex folding/assembly patterns, such as immunoglobulins? In collaboration with the Toxin Group, these questions are addressed in vivo by studying the intracellular fate of model secretory proteins, such as the plant toxin ricin, a secretory immunoglobulin A and the storage protein phaseolin. These studies employ biochemistry, cell biology and proteomic techniques.
ER shape and function: we have recently initiated the study of the plant reticulon family. Reticulons have been described as major regulators of ER shape in mammalian and yeast cells. The Arabidopsis genome contains 21 members of the reticulon family. We analysed the smallest isoform, RTNLB13, and found that its overexpression in plant cells constricts the ER tubules, thus limiting diffusion of soluble proteins in the ER lumen. In collaboration with Prof Chris Hawes (Oxford Brookes), we are now assessing the effect of reticulon overexpression on the overall function of the anterograde secretory pathway.

TEACHING PROFILE

Courses Taught

• BS273- Cell Biology II
• BS364 - Post Genomic Research
• BS318 - Protein Targeting
• BS110 - Animal and Plant Biology
• BS248 - Plant Molecular Development
• BS129 - Physiology and Metabolism

RESEARCH PROJECTS

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SELECTED PUBLICATIONS

• Denecke J, Aniento F, Frigerio L, Hawes C, Hwang I, Mathur J, Neuhaus J-M, Robinson DG(2012) 'Secretory pathway research: the more experimental systems, the better' The Plant Cell (1040-4651) [article]
• Scheuring D, Viotti C, Bubeck J, Kruger F, Sturm S, Frigerio L, Robinson DG, Pimpl P, Schumacher K(2011) 'Multivesicular Bodies Mature from the Trans-Golgi Network/Early Endosome in Arabidopsis' The Plant Cell (1040-4651) [article]
• Gattolin, S., Sorieul, M. and Frigerio, L.(2011) 'Mapping of tonoplast intrinsic proteins in maturing and germinating Arabidopsis seeds reveals dual localisation of embryonic TIPs to the tonoplast and plasma membrane' Molecular Plant 4 180 - 189 (1674-2052) [article]
• Sorieul M, Langhans M, Guetzoyan, L, Hillmer S, Clarkson G, Lord JM, Roberts LM, Robinson DG, Spooner RA, Frigerio L(2011) 'An Exo2 derivative affects ER and Golgi morphology and vacuolar sorting in a tissue-specific manner in Arabidopsis' Traffic (1398-9219) [article]
• Wang P, Hummel E, Osterrieder A, Meyer A, Frigerio L, Sparkes I, Hawes C(2011) 'KMS1 and KMS2, two plant endoplasmic reticulum proteins involved in the early secretory pathway' Plant Journal, The 66 613 - 628 (0960-7412) [article]

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