| Phospholipase D 3 (PLD3) is an atypical and uncharacterized member of the phospholipase D (PLD) superfamily. First discovered as the mammalian homologue of the vaccinia virus K4L protein, PLD3 is a type II glycoprotein associated with the endoplasmic reticulum. PLD3 is expressed in a wide range of tissues and cells, including neural and skeletal especially during differentiation events. To date, there are no published reports describing a cellular function or biochemical activity for PLD3. Very little information can be deciphered from vK4L because it is not essential to the viral life cycle. The closest homologue of mammalian PLD3 with a known function is the vaccinina virus F13L protein. Like other members of the PLD superfamily, F13L is involved in membrane trafficking and fusion events. Specifically, F13L is involved in wrapping viral particle is post --Golgi vesicles, presumptively, through broad spectrum lipase activity.;Using an in vitro skeletal muscle differentiation system, I have demonstrated that overexpressed PLD3 enhances myotube formation in differentiating myoblasts, a phenotype that may be associated with the ER-stress response. Knockdown of PLD3 expression via RNAi, lead to decreased cell fusion, increased cell death and, paradoxically, a significant increase in PLD3 expression over time. Using indirect immunofluorescence and exhaustive colocalization studies, I observed that PLD3 protein localizes to unknown intracellular vesicles, which may be derived from the endoplasmic reticulum. These findings suggest that PLD3 plays a role in myogenesis and may be involved in cell viability and myotube formation. |
