A photoaffinity probe for the cardiac adenosine transporter

Area of Science:

• Biochemistry
• Molecular Biology
• Cardiovascular Research

Background:

• Adenosine transport is crucial for cardiac function and energy metabolism.
• Identifying the specific protein responsible for adenosine transport in the heart remains a challenge.

Purpose of the Study:

• To develop and utilize a photoaffinity probe to identify the adenosine transporter in cardiac sarcolemmal (SL) vesicles.
• To characterize the molecular weight of the cardiac adenosine transporter.

Main Methods:

• Synthesis of an azidosalicylate derivative of adenosine as a photoaffinity probe (ASA-adenosine).
• Radiolabeling of the probe with Iodine-125 and purification using high-performance liquid chromatography.
• UV irradiation of cardiac SL vesicles with the labeled probe to induce covalent labeling.

Main Results:

• The photoaffinity probe (125I-ASA-adenosine) covalently labeled a 65 kDa protein in bovine cardiac SL vesicles upon UV irradiation.
• Labeling of the 65 kDa protein was significantly reduced by known inhibitors of purine nucleoside transport, such as adenosine and guanosine.
• Glucose, a non-inhibitor, did not affect the labeling, confirming specificity.

Conclusions:

• The cardiac adenosine transporter is identified as a protein with an apparent molecular weight of 65 kDa.
• This study provides molecular identification of a key transporter involved in cardiac adenosine uptake.