• Lipoprotein & protease receptors
• cell migration
• Alzheimer disease
• Vascular biology
• PDGF receptor
• macrophages and their role in inflammation

The low density lipoprotein (LDL) receptor-related protein (LRP) is a large cellular receptor that not only functions as important cargo transporters, but also informs the cell of changes in its environment by mediating signaling responses.  LRP is a member of the LDL receptor superfamily, and binds 30 or more ligands.  Their cargo transport by LRP is closely associated with regulation of cellular physiology and cellular signaling events.  A goal of studies in our laboratory is to understand the role of LRP in modulating cell signaling events and how this affects development of certain diseases.  

Role of LRP in atherosclerosis.  Smooth muscle cells play an important role in the maintenance of vessel wall integrity, and undergo proliferation in response to injury.  Interestingly, a role for LRP in smooth muscle biology was established some time ago, when it was demonstrated that LRP antibodies inhibited smooth muscle cell migration.  More recent studies have found that LRP is atheroprotective, and prevents proliferation of smooth muscle cells in response to injury.  This occurs by regulation of platelet derived growth factor (PDGF) receptor, a receptor tyrosine kinase that is activated upon binding PDFG.   PDGF induces a transient tyrosine phosphorylation of the LRP cytoplasmic domain in a process dependent on PDGF receptor activation, and may have important consequences in PDGF initiated signaling.  Studies are now underway to identify the functional role LRP plays in modulating PDGF signaling pathways. 

Role in inflammation.  Chronic inflammation is a key feature of atherosclerosis.  During the development of this disease, monocytes are recruited to the vessel wall where they differentiate into macrophages and greatly accelerate plaque formation and the progression of this disease.  Many ligands recognized by LRP are generated during inflammation and/or wound repair, which has led us to hypothesize that LRP functions to modulate the inflammatory response, and our laboratory is investigating this hypothesis by studying the role of LRP in macrophages.

Role of LRP in Alzheimers disease.  The brain of an Alzheimer patient is marked by two major abnormalities: neurofibrillary tangles and amyloid (or senile) plaques. Neurofibrillary tangles are bundles of protein filaments found inside nerve cells, and senile plaques are clusters of amyloid surrounded by dead or dying cells. These plaques are mainly composed of a small peptide, called beta amyloid (Abeta), which is derived from a much larger precursor protein called beta amyloid precursor protein (APP). Other than manufacturing the protein that becomes a plaque that can lead to Alzheimer disease, the function of APP in the body is unknown.  Abeta deposition is an important pathological step in Alzheimer disease, and reflects an imbalance of Abeta synthesis and clearance.  Several pathways that impact Abeta production and clearance converge on LRP.  This multifunctional receptor can help clear Abeta peptide under certain conditions, while under other conditions can increase production of this peptide.  Studies in the laboratory are currently underway to investigate these pathways.