Department of Pharmaceutical Sciences
University of Tennessee Health Science Center
Memphis, TN

BASIC RESEARCH PROJECT

CD5L-mediated Autophagocytosis in RPE cells

Research Interests

Scientific Summary:  Dr. Giorgianni has discovered that patients affected by an elderly eye disease, called age-related macular degeneration (AMD) that compromises their vision, have antibodies circulating in their blood that can attack and damage proteins present in the eye. One of these proteins, that may be targeted by the circulating antibodies, might be important for the removal of compounds toxic to the eye.

In Dr. Giorgianni’s proposed project, he will plan to carry out experiments to demonstrate the function of this protein, called CD5L, in the retinal pigment epithelium (RPE), a type of cell that is compromised in AMD patients. Dr. Giorgianni believes that CD5L functions as a carrier of toxic compounds, especially those derived from cholesterol, and facilitates these toxic compounds’ degradation, which in turn prevents their accumulation and resulting damage to the RPE.

The Giorgianni lab will perform experiments to prove that the presence of CD5L inside the RPE cells accelerates the degradation of a compound, derived from cholesterol, called OxLDL. Lab members will also identify other proteins that are needed together with CD5L to perform the degradation of toxic OxLDL. To accomplish this, the team will leverage analytical tools (mass spectrometer) available in their laboratory that can quickly identify and quantify proteins. The findings from the proposed studies will help to better understand the cellular mechanisms that lead to AMD and could provide new leads for the development of new therapeutic strategies.

Plans for 2024

We propose to determine the function of CD5L (CD5 antigen-like), a secreted glycoprotein, member of the scavenger receptor cysteine-rich (SRCR) superfamily, in human RPE cells. Recent data obtained in our laboratory show that ARPE-19 cells (a human RPE-derived cell line) in the presence of recombinant human CD5L (rhCD5L) display a significant, time-dependent, decrease in intracellular accumulation of OxLDL, which suggests activation of intracellular degradation processes. Furthermore, ARPE-19 cells expressing rhCD5L show a similar decrease in intracellular OxLDL accumulation as compared to controls lacking rhCD5L. These observations suggest that CD5L might play a significant role in OxLDL clearance by the RPE. Specifically, we hypothesize that CD5L facilitates the removal of intracellular OxLDL and plays a role against oxidative damage in RPE cells. This clearance mechanism involves the formation of CD5L-OxLDL intracellular macromolecular complexes and the activation of autophagy mechanisms that result in the degradation of OxLDL.

Specific Aim 1: To determine the role of endogenously expressed CD5L in RPE cells as a cytoprotective agent against OxLDL-mediated oxidative damage through facilitation of autophagy.  a) Test the hypothesis that CD5L is cytoprotective and helps RPE cells maintain their normal physiological state when exposed to OxLDL; b) Test the hypothesis  that CD5L promotes OxLDL cellular clearance through autophagy mechanisms.

Specific Aim 2: To characterize the molecular interactions between endogenously expressed CD5L and other proteins that mediate the activation of autophagy processes. a) Test the hypothesis that the intracellular CD5L-OxLDL complex generates specific and time-dependent gene transcription and proteome profiles; b) Test the hypothesis that intracellular CD5L-OxLDL complexes mediate protein-protein interactions that promote OxLDL processing and clearance; c) Test the hypothesis that intracellular CD5L-OxLDL complexes induce specific changes in the ubiquitome of RPE cells that differs from the OxLDL-only treated cells.

Progress in 2023

The data Dr. Giorgianni generated during 2023 are part of two published manuscripts and of a third manuscript in preparation. The first manuscript focusing on the transcriptome analysis was published in the International Journal of Molecular Sciences. A second manuscript which reports on the proteomics studies was published in Biochemistry and Biophysics Reports. The manuscript in preparation focuses on Dr. Giorgianni’s our latest findings related to the induction of protein ubiquitination and the interaction of CD5L with HSPA8 in RPE cells following OxLDL treatment.

Specifically in 2023, Dr. Giorgianni researched the hypothesis that CD5L facilitates the removal of intracellular OxLDL and plays a role against oxidative damage in RPE cells. This clearance mechanism involves the formation of CD5L-OxLDL intracellular macromolecular complexes and the activation of autophagy mechanisms that result in the degradation of OxLDL.

Specific Aims:
Aim 1. To determine the role of endogenously expressed CD5L in RPE cells as a cytoprotective agent against OxLDL-mediated oxidative damage through facilitation of autophagy by: a) Test the hypothesis that CD5L is cytoprotective and helps RPE cells maintain their normal physiological state when exposed to OxLDL; b) Test the hypothesis that CD5L promotes OxLDL cellular clearance through autophagy mechanisms.
Aim 2. To characterize the molecular interactions between endogenously expressed CD5L and other proteins that mediate the activation of autophagy processes by: a) Test the hypothesis that the intracellular CD5L-OxLDL complex generates specific and time-dependent gene transcription and proteome profiles; b) Test the hypothesis that intracellular CD5L-OxLDL complexes mediate protein-protein interactions that promote OxLDL processing and clearance; c) Test the hypothesis that intracellular CD5L-OxLDL complexes induce specific changes in the ubiquitome of RPE cells that differs from the OxLDL-only treated cells.

2023 Publications

Progress in 2022

Significant progress in understanding the role of CD5L was made in 2022.  Importantly, Dr. Giorgianni’s research data showed that in response to OxLDL, CD5L migrates to the apical side, the interior side, of differentiated RPE cells. This finding could have major implications in the understanding of cellular clearing mechanisms in RPE cells related to AMD. Dr. Giorgianni’s research data gathered in 2022 was part of two manuscripts. The first manuscript focusing on the transcriptome analysis was published in the International Journal of Molecular Sciences. A second manuscript which reports on the proteomics studies was published in Biochemistry and Biophysics Reports.

Progress in 2021

In 2021, Dr. Giorgianni carried  out studies to demonstrate the function of the protein, CD5L, in the retinal pigment epithelium (RPE), a type of cell that is compromised in AMD patients. He believes that CD5L functions as a carrier of toxic compounds, especially those derived from cholesterol, and that facilitates their degradation thus preventing their accumulation and damage to the RPE. Experiments were performed  to prove that the presence of CD5L inside the RPE cells accelerates the degradation of a compound, derived from cholesterol, called OxLDL. Additionally, Dr. Giorgianni identified other proteins that are needed together with CD5L to perform the degradation of toxic OxLDL. For this part of the project, the lab leveraged their new analytical tools that can quickly identify and quantify proteins.

Progress in 2020

Despite delays resulting from the coronavirus pandemic, Dr. Giorgianni’s progress findings were submitted to two publications, resulting in one manuscript publication in the International Journal of Molecular Sciences in November, 2020.  A second manuscript reporting on the proeomics studies was submitted in November, 2020.