(1) The various retirement system funds, as established in the State Treasury, are created and constituted trust funds.
(2) All assets of the various funds, both cash and securities, shall be under the exclusive jurisdiction of the respective boards of trustees and shall be held by the Treasurer of State as custodian, subject to the orders and direction of the boards of trustees.
(3) The interest received on all investments made from the trust funds shall be considered as trust fund income and shall be deposited into the State Treasury to the credit of the retirement system fund from which the investments were made.