Assistant Professor, Biological Sciences Carnegie Mellon University Phone: 412-268-8236 Fax: 412-268-7129 Email: map3@andrew.cmu.edu

Ph. D., Carnegie Mellon University

Research Interests

Why do we get addicted to drugs? Opioid drugs (like heroin and morphine) activate the same receptors and signaling pathways in the brain as activated by endogenous opioid peptides (like endorphins).  But we rapidly develop tolerance and dependence to drugs, but far less so to endogenous opioid peptides. The meager clues we have point towards differences in the regulatory events that follow receptor activation as the culprit.  

Intracellular trafficking of opioid receptors is such a critical regulatory event that might play a role in the development of drug addiction. Despite this significance, we know very little about how trafficking of receptors regulates their signaling, and vice versa.  Therefore, research in the lab uses opioid receptors and related G protein-coupled receptors (GPCRs) as examples to investigate 1) the molecular mechanisms that mediate trafficking of signaling receptors, 2) the regulatory events that control these mechanisms, and 3) the functional consequences of these regulatory events at the level of the neuron and the brain.

Specific projects:

• Regulation of opioid receptor endocytosis by addictive drugs
  Activation of opioid and related GPCRs results in removal of activated receptors from the cell surface via endocytosis through clathrin-coated pits, leading to de-sensitization of the cell to the signal. Receptors were long thought to be passive ‘cargo’ in this endocytic process. Our recent data, however, suggest that receptors play a more active role in controlling their own destiny, by specifically regulating the kinetics of the subset of clathrin-coated pits that they use. We are investigating the mechanisms by which opioid receptors, when activated by drugs, regulate endocytic kinetics. These mechanisms likely play a key role in drug addiction, because the amount of receptor endocytosis induced by drugs seem to be linked to their addictive potential.
• Sorting of signaling receptors in the endosome.
  Endocytosed receptors may either be returned (or recycled) to the cell surface, thus allowing the cell to respond to the signal again (i.e., be ‘re-sensitized’ to the signal), or be targeted to the lysosome to be destroyed, leading to prolonged ‘de-sensitization’ of the cell. Despite this clear significance to signaling, how different receptors are sorted from one another in the endosome and packaged into distinct trafficking pathways is not known. We have identified a novel role for an actin-based machinery in selectively directing specific signaling receptors to the recycling pathway, and are investigating the biochemical mechanism, regulation, and functional relevance of this machinery.
• Regulated surface insertion of receptors from the biosynthetic pathway.
  In the case of receptors that are not recycled, the cell is re-sensitized only when newly synthesized receptors are inserted on the plasma membrane from the biosynthetic pathway. While there is evidence that biosynthetic insertion of receptors is highly regulated in neurons, we know very little about the signaling mechanisms that regulate this insertion and their functional significance. We use the delta-opioid receptor, whose biosynthetic trafficking is regulated, as a model receptor to study the general principles, mechanisms, and functional consequences of regulated insertion of signaling receptors on the plasma membrane.

Recent Publications

• Puthenveedu MA, et al: Sequence-dependent sorting of recycling proteins by actin-stabilized endosomal microdomains. (In revision).
• Yudowski GA*, Puthenveedu MA*, Henry AG, von Zastrow M: Cargo-mediated regulation of a rapid Rab4-dependent recycling pathway.  Mol Biol Cell 20(11):2774-84, 2009. *denotes equal authorship
• Yudowski GA*, Puthenveedu MA*, Leonoudakis D, Panicker S, Thorn KS, Beattie EC, von Zastrow M: Real-time imaging of discrete exocytic events mediating surface delivery of AMPA receptors. J Neurosci 27(41):11112-21, 2007.  *denotes equal authorship
• Puthenveedu MA, Yudowski GA, von Zastrow M: Endocytosis of neurotransmitter receptors: location matters. Cell 130(6):988-9, 2007.
• Shaw RM, Fay AJ, Puthenveedu MA, von Zastrow M, Jan YN, Jan LY: Microtubule plus-end-tracking proteins target gap junctions directly from the cell interior to adherens junctions. Cell 128(3):547-60, 2007.
• Puthenveedu MA, von Zastrow M: Cargo regulates clathrin-coated pit dynamics. Cell 127(1):113-24, 2006.
• Yudowski GA, Puthenveedu MA, von Zastrow M:  Distinct modes of regulated receptor insertion to the somatodendritic plasma membrane. Nat Neurosci 9(5):622-7, 2006.